Well, in my case - I use some client-side mods on the latest version (1.15.2) like minimap and hwyla just to make it more comfortable to play. So, this client won't ruin my saves and so on. I also use it to play on some vanilla servers. I use this client to play as well as I do on a vanilla one.
So, that's why I need to keep my saves, screenshots and so in the same folder with other game versions. Is it possible somehow? Or is there any possibility of returning this feature with version-specific mod folders back?