I have been using an in-house/handrolled physics engine for the last few years so not sure if something has changed, but being able to modify the physics engine for arcade or other non-realistic style games was a big let down over time as well. Basically optimizing your game for feel was quite hard with Box2D in general.

For a long time there wasn't deformers in Box2D (not sure if it's in there now), I hacked by own but I was a dumb 17yo and it was a horrid mess back in the day. Maybe AI could do better than the old me, but I gave up pretty quickly after not getting good results.

So basically lack of support for non-rigid bodies and lack of easy customisability made it not age well for someone like me.

But I know people who have had performance issues with it when building large maps/worlds as well so there are other issues.

Again all of these could have been fixed if they paid more attention to it, more dev time, but it was free so I couldn't really ask for more as a broke student.

And best part was you could run it on any hardware, I remember cooking up a small 2d demo on a rpi back in the day. Fun times.