On some of the older devices, nouveau actually works very well right now. On these devices the open driver is as stable and performant as the closed driver and has all of the same features with the exception being GPU compute stuff.
I think mostly people misunderstand the limitations of the nouveau drivers and just assume they are bad in general, but it's very much dependent on the device.
One of the big issues right now is that nouveau can't bring the newer GPUs out of "idle mode". Nvidia has explicitly restricted this feature and the chances of the issue being resolved without cooperation from Nvidia is very low. I think a lot of people try nouveau on the effected GPUs and have horrible performance and then assume it's because nouveau is bad.
I have had an interesting experience with nouveau on the GT 710. For a little while there was a bug that would cause sway to crash back to tty, at first it would happen maybe once a day, then it became so bad that it would crash as soon as sway was launched. Now in kernel 6.3.3 it seems to be working flawlessly, which is how it was at some point in the past too.
Right now nouveau is working great for me though, so it is possible for nouveau to compete with the closed drivers in specific cases, but in general, for more modern GPUs it will have very low performance due to the reclocking thing.