I agree with mike that this could be a whole post on its own, but something that’s helped me pare down the pile of potentials was the rough guidelines that both Prof (TCC) and Tomer (Goldfish) put out a couple of years ago, where they talk about how much ramp vs removal vs card draw you should aim for (I still try to run at least one “you win the game” card in every deck, in line with Tomer’s suggestion).
I still review my 99 with that in mind, even if I don’t always hit those exact numbers, and it’s helped make my decks play more smoothly whenever I run them, and is also really helpful when upgrading, since I know if I’m adding a new card draw engine, then my cuts should be from my existing card draw.
It’s probably helpful if I actually share the links:
TCC - How to Build Your 1st Commander Deck: https://youtu.be/1jO2fmsef0g
MTGGoldfish - https://www.mtggoldfish.com/articles/the-power-of-a-deckbuilding-checklist-commander-quickie