Frankly, I don't like almost anything about it. The dynamic loading/endless scrolling instead of pages, the silly navigation bar, the "x time later" instead of the exact date and time, the narrow post width...

I get "dumbed-down, mobile first" vibes from the UI, kinda like Twitter, which is the last thing I want for a forum with thoughtful discussions. And it's also more bloated/slower than classic forums (https://danluu.com/slow-device/).

I think the best forum software right now is XenForo. But even phpBB and many similar free alternatives (MyBB, SMF,...) are better than Discourse. Those can also be heavily customized (might be true for Discourse too, but I doubt it would improve it much).