How much has modding changed since 1.21?

I'm deciding what version to make my mod for, but NOT the typical post I always see here. I don't care what version is most popular or has "the best mods" or any of that. I am curious though how modding has changed on a technical level. I don't really like a lot of the recent content changes/additions so I was thinking of making a 1.20.1 or 1.21.4 mod but I know mojang has done a lot lately with de-obfuscation, vulkan rendering, and especially: more data driven features.

How have these things ACTUALLY affected modding so far? have they made things a lot easier? Made new things possible that weren't before? Or expanded the horizons of modding as a whole? Or has it mostly just affected the back end stuff that is primarily dealt with by the mod loaders?

If you actually work on mods or have heard direct info from people who do I would love to know more about the topic but please no speculation based on hearsay