So I have been spending all the time I can re-rating my iTunes Library, and so far I am only in D! This is going to literally take forever! Such a pain. And it seems to have been slowing down the more things I rate or make playlists, but that seems to have changed.
iTunes updated to version 12.3.2.35 recently, which allows for 100,000 songs in iTunes Match, and iTunes seems to have sped up again, no more beachballs all the time. Nice! Lets hope it stays this way! This is such an improvement. My almost 50,000 library seems zippy again!