I've bought at least 1 version of everything except the adventure paths - and it has all been of use. I tend to not buy adventure paths, although I buy chapters from them on D&D beyond to get access to the materials for use in my games.
I have a shelf full of official 5E D&D books, but I have used only half of them at most (and I stopped automatically buying all of them about 3 years ago, choosing the ones I think I'll use now). Then again I have 10 x that number of RPGs total, many of which I've never had chance to play. That's OK -- I like reading RPGs!
How many official 5E D&D books have you got?
How many of those have you used?