I can't speak to what it was at release, but I just recently returned to the game and played SE for the first time. I've played heavily modded for over 30 hrs and had VERY few issues. If it's a "broken mess of bugs" I've not experienced it. I've only encountered one mod so far that gave me major issues. LOOT is better than it's ever been and I've only had to manually reorder 2 mods (1 if you don't include the aforementioned broken mod). Seems like a really good time to be working on SE from a predominantly player standpoint.
FPS issues because of plugins existing in the load order, visual issues because of plugins modifying large references, broken tree LOD reflections, the "improved" snow shader that is an incoherent and incomplete mess, game randomly not starting because of CC connection issues or whatever. Also stuff like hardcoded key bindings, sprint toggle, enemy perks applying twice after loading, plants not re-spawning after loading etc.
The issue is that Bethesda is actively updating the game to serve as a platform for paid mods and yet there still seems to be a believe that it is acceptable to rely on the community to provide free fixes to make this game version somewhat usable for modding. On the other hand, there is a perfectly stable and tons of better looking and feature rich Skryim without any such dilemmas.
My point is, as long as there are so many severe bugs which need to be fixed by Bethesda, there is no reason to waste any more time than necessary for things that should/can change over night. In particular, there is no use testing any mods/plugins that modify large references. Unless the large reference bugs are fixed, those plugins are incompatible with Skyrim SE.