For me, it's the lack of mobile view. I like this place, more than any website I use (and I use a lot) but having to zoom in and out and move the screen with the text to read is just as painful as nails on chalkboard.
That's your perspective. Doesn’t mean that everyone else have the same feelings too. I have used the forum from both mobile and PC. I barely use this forum from PC these days though I used to use PC more back in the day. Now, I only log in from PC when I create a thread. Otherwise, I can read, write from mobile and feel comfortable enough.