This seems like an incredibly low bar to hurdle. FB Messenger on iOS is legendarily bloated. In the couple of weeks I had it installed it also managed to be the biggest battery drain on my phone, even more than some 3D games.
It may have been slow and bulky before that, but that's when I started to notice.
Aren't those using Electron?
tl;dr web clients are probably more performant than their electron counterpart
It's unreal, our industry has lost its mind.