Common frustration with updates to commands!

While this post has the same title as another, it is different to it

Commonly, people build their commands around a Recent Version, with it's own specific Command Systems; but these get updated way too drastically, and too often.

If you could, update the Commands so they are better, but don't mess with older commands completely. 
As I made a Custom Villager with items available for trade, in which had custom text for each with their own NBT data; 1.21.5+ messed it up completely, and it is very frustrating.