I’m pretty convinced that a lot of CTD errors people get are due to their own system configurations. In some cases, it’s people with heavy overclocks that claim “all my other stuff runs fine” or in cases like yourself, that the RAM may be rated to a certain speed, but for whatever reason, its timings just aren’t quite in spec. Even though it may perform well with everything else, MSFS doesn’t like it.
In my case, I can overclock my CPU to 4.2 GHz on all cores (Ryzen 2700X - that’s 100MHz higher than it’s top boost of 4.1 GHz). It passes all stress tests, and works in all my games and other CPU-intensive apps. But MSFS will crash hard. If I step it back to 4.1 GHz (its top rated speed), it doesn’t crash, but I get stutters and weirdness in sim. Rolling it back to 4 GHz, or just setting Precision Boost to Auto, and it runs just fine, in some cases, boosting to 4.1 GHz (not on all cores though) without issue.
My memory is similar to yours. It’s rated at 3000 MHz. At full speed, it runs fine most of the time, but causes instability in memory instensive applications. Most of the time things work well, but will get the occasional app crash or even BSOD. If I step it down 1 notch to 2666 MHz, everything works fine.
Now in no way am I saying that there aren’t some legitimate serious bugs in MSFS and it’s all users’ fault, but a lot of stuff that gets reported is likely self-inflicted, and it some cases, users may not even know it. You’re an example here. You were running your RAM at its rated speed and having issues that were solved stepping it back 1 notch.