Hi Tulrin,
Welcome to the Mattress Forum! … and I’m glad you found us 
Your mattress has lower quality and less durable materials than I would normally suggest so it’s not surprising that it had a shorter useful life as well. You were probably fortunate that you were able to get 5 years of use from it.
There is more information about motion transfer relative to different materials and types of mattresses in post #18 here. You are right that in general terms memory foam is the most effective material in terms of isolating motion.
While I can certainly help with “how” to choose … It’s not possible to make specific suggestions or recommendations for either a mattress, manufacturers/retailers, or combinations of materials or components because the first “rule” of mattress shopping is to always remember that you are the only one that can feel what you feel on a mattress and there are too many unknowns, variables, and personal preferences involved that are unique to each person to use a formula or for anyone to be able to predict or make a specific suggestion or recommendation about which mattress or combination of materials and components or which type of mattress would be the best “match” for you in terms of “comfort”, firmness, or PPP (Posture and alignment, Pressure relief, and your own Personal preferences) or how a mattress will “feel” or compare to another mattress based on specs (either yours or a mattress), sleeping positions, health conditions, or “theory at a distance” that can possibly be more reliable than your own careful testing (hopefully using the testing guidelines in step 4 of the tutorial) or your own personal sleeping experience (see mattress firmness/comfort levels in post #2 here).
I’m not sure what you’ve read since you found the site but just in case you haven’t read it yet … the first place to start your research is the mattress shopping tutorial here which includes all the basic information, steps, and guidelines that can help you make the best possible choice … and perhaps more importantly know how and why to avoid the worst ones.
Two of the most important links in the tutorial that I would especially make sure you’ve read are post #2 here which has more about the different ways to choose a suitable mattress (either locally or online) that is the best “match” for you in terms of “comfort”, firmness, and PPP that can help you assess and minimize the risks of making a choice that doesn’t turn out as well as you hoped for and post #13 here which has more about the most important parts of the “value” of a mattress purchase which can help you make more meaningful quality/value comparisons between mattresses in terms of suitability (how well he will sleep), durability (how long he will sleep well), and the overall value of a mattress compared to your other finalists based on all the parts of your personal value equation that are most important to you (including the price of course and the options you have available after a purchase if your choice doesn’t turn out as well as you hoped for).
If you are considering online options that you can’t test in person before a purchase then the mattress shopping tutorial includes several links to lists of many of the better online options I’m aware of (in the optional online step) that include many different types and categories of mattresses that use different materials and components in a wide range of designs, budgets, firmness levels, and with different return/exchange policies that may be well worth considering as well.
One of the lists includes many of the better online memory foam options I’m aware of and many of these are well inside your budget range as well.
If you would also like to do some local testing where you can test a mattress for motion transfer in person before a purchase then if you let me know your city or zip code I’d be happy to let you know about the better options or possibilities I’m aware of in your area.
While again nobody can speak to how any specific mattress will “feel” for someone else or whether it will be a good “match” in terms of comfort, firmness, and PPP because this is too subjective and relative to different body types, sleeping positions, and individual preferences, sensitivities, and circumstances and you are the only one that can feel what you feel on a mattress … outside of PPP (which is the most important part of “value”), the next most important part of the value of a mattress purchase is durability which is all about how long you will sleep well on a mattress. This is the part of your research that you can’t see or “feel” and assessing the durability and useful life of a mattress depends on knowing the specifics of its construction and the type and quality of the materials inside it regardless of the name of the manufacturer on the label or how a mattress feels in a showroom or when it is relatively new so I would always make sure that you find out information listed here so you can compare the materials and components to the durability guidelines here to make sure there are no lower quality materials or weak links in a mattress that would be a cause for concern relative to the durability and useful life of a mattress before making any purchase.
There are some comments about all of the mattresses you listed in post #2 here in the simplified choice topic along with many of the other simplified choice mattresses as well and post #1 in the same topic would be well worth reading as well.
With the exception of the Leesa which uses 2" of 3 lb memory foam … there are no lower quality materials or weak links that would compromise the durability or useful life of any of the mattresses you listed. The 3 lb memory foam in the Leesa is underneath 2" of polyfoam which would absorb some of the compression forces that come from sleeping on a mattress which would improve the durability of the 3 lb memory foam underneath it a little so while it may be more risky than the others in terms of durability … with your lighter BMI the odds would be higher that it will maintain it’s comfort and support for a reasonable length of time as well.
When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using (fast or slow response, resilience, firmness etc) and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else.
Having said that … mattresses that have memory foam as the top layer would have the higher odds of having the least amount of motion transfer than mattresses that use more resilient materials in the top layer and thicker layers of memory foam may be more effective than thinner layers as well but there are also differences between different memory foam formulations and mattress designs so the only way to know for certain whether any mattress is “motion isolating enough” for you will be based on your own careful testing or your own personal experience when you sleep on it.
One of the advantages of trying mattresses locally is that you can try many different types and styles and firmness levels and compare them to each other in “real time” based on your actual experience rather than just “theory” instead of trying one mattress and not knowing how it compares to the other mattresses that you could have tried or purchased instead.
Of course many online mattresses have a good trial period and return policy so you can try them in your bedroom instead of a showroom with little risk (outside of the time you spend sleeping on it and/or returning it if that becomes necessary or any costs involved in the return process) so if it’s not a “good enough” match for you in terms of comfort, firmness, and PPP (including motion transfer) you can just return it and try another mattress although of course you will only know whether it’s “good enough” and you won’t know whether it would have been better or worse or how it compares to other mattresses that you could have purchased that you haven’t tried in person.
Phoenix