Haters aren't worth listening to. Doesn't matter if it is flatpak, systemd, wayland, or whatever else. These people have no interest in a discussion about merits and drawbacks of a given solution. They just want to be angry about something.
Wayland gets the hate because compositors are authoritative so you cannot e.g. install your own window manager, taskbar, etc. It would be good if there were specifications governing these, but there isn't.
I know, right!? Add gimp to that list as well. I can go on and on about shortcomings of gimp despite being a happy user. The average gimp hater, on the other hand, doesn't have anything to say besides "the UI is dumb and I can't figure out how to draw a circle"
kate editor would like to have a word... They did my lady kate dirty with the latest updates :( The top level File menu was so much better and now I don't know where to find the configuration to get that back, and have on my work computer a stupid single button in the top right corner which opens the "menu bar", except vertically..