Depends how far back you go. Obvs, not all mods are keeping up as the game updates, but if anything, I find that the modding community has only every grown and gotten better with time.

I think that mod versioning was introduced in 1.1 (so about when Royalty released), which made it a lot easier to keep track of what works and what doesn't, so you might have issues with mods from before then, but honestly there'll almost certainly be a replacement if something was popular and was discontinued.