The only defense against copies has always be the same, be better than the copies in thing the consumer likes. You can't copy a Mario game, you can't copy a Kojima game, you can't copy a game that has been masterfully done and polished. If slop is gonna eat your lunch, it's only because your game is as good as slop.
Sure if you made a name for yourself, you can bank on that. People will buy Slay the Spire 2 instead is cheap copycats.
However I you are a new indie dev and made a decent game, how can people find you? They can't under the sea of slop. They could scroll and scroll and never find you.
I heart from many game reviewers that they have an harder and harder time finding good games to review. Not because people don't make good games anymore, in fact more good games than ever are made but finding them is harder than ever. Indie devs don't have a giant marketing department.
If steam keeps refusing to curate game the gaming market is going to crash hard.