That is true. I do feel like whenever there's a general RPG group, it usually breaks down quickly into every post either being related to 5E, or complaining about 5E.
I stopped visiting RPG on Reddit because it felt like half the posts were just complaining about 5E, and while I don't disagree with those posts, I would rather talk about the things I DO enjoy.
I only consider it too many when it becomes a burden. If you're spending a fortune on Zine Quest but struggle to pay your grocery bills that month, maybe it's too many books. If your book shelves are all full and you've run out of space in your home to add additional book shelves, maybe it's too many books.
And of course, i f you yourself feel like the engagement with most of your collection is unsatisfying, then too, maybe it's too many books. It might sound stupid and like a stereotype, but ask yourself "does this book spark joy?" If yes, it's not too much. If no, get rid of it.
Personally I have quite a large collection - about as large as I can go, as I actually reached the point where I'm literally running out of space in my home. But my pile of shame is tiny thanks to me GMing 2-3 game sessions a week, so I'm still getting joy from over 90% of my collection.