There is no hard rule to these things because something that often gets overlooked is that while inferior drives have inferior results, they also cost less and not all use cases will be ones where those lower results matter. So sometimes the tradeoff has merit.
It's easy to just get a high end drive and call it a day but that's not always necessary... especially for a games drive of all things. Maybe the year of DirectStorage eventually, finally happens on a large scale and changes this, but as of today, it doesn't matter for most games. DRAM or a lack of it doesn't make a difference with read performance; only with write performance. Most of gaming will be reads. For the same reason, you're unlikely to wear them out (DRAM also adds to longevity).
How good a drive is comes down to many things, not simply if it has DRAM or not. There aren't really real world examples of "the same drive with and without DRAM" so it tends to be hard to isolate exactly, as drives without DRAM also tend to be lower end in other ways (QLC instead of TLC, lower SLC cache portion, slower controllers, etc.). This is also a bit of a holdover from the early SATA days, where drives without DRAM were really horrible. It still matters, but less so on NVMe.
One relatively minor mention that I'll make is that with Steam in particular, some drives that are generally performant but lack DRAM seem to slow way down during the initial download and installation process. The workaround is to download it to another drive, even an HDD instead, and then move it over. If you want to rule that out, no matter what, maybe give a thought to DRAM.
