This is part of why I say I don't believe 5.5e has anything more than about 6, maaaaybe 7 years in it.
Some of it is just "why should I bother". Some of it is "I don't like the changes."
But I think the biggest thing is that 5.5e is mostly, but not entirely, "more of the same" while calling attention to parts of "the same" that maybe didn't work as well as people had hoped. Its existence means the honeymoon has mostly worn off, and the fact that it's the same but different but the same means people will be thinking about the differences and also asking, "Well...what would I do differently?"
Between that and just...the system being old at that point, 15+ years is a LONG time for a system, any system, especially one with the, let's say "particular" things 5e contains. 1e->2e managed to make a mostly-the-same system last for a whopping 25 years, and much of that was simply because the internet didn't exist. In our modern, hyperconnected age, I don't think a single edition of D&D will ever last more than 15 years in most cases, and 20 years at absolute maximum. That's enough time for a new generation of designers, a new generation of fans, and both of those wanting change.