Is it the hours? Unrealistic expectations around work output? Hostile management or colleagues? Outcomes you are responsible for but don't fully control? Sometimes it's something MISSING, like you don't feel meaning in the work anymore, a strong feeling of being "over it".

There's a lot of misery in working for places that are too big (drowning in process, politics, management halls of mirrors) or too small (you are basically at the whim of one or two other people and you're very closely watched).

For good power relations with a company and colleagues you ideally want your leverage to be as equal as possible. You don't want to be completely disposable, and you don't want to be irreplaceable. You want the company to hurt approximately as much finding a replacement as you do getting another job.

The hard thing about pure software companies IMHO is that it's easy to feel distant from any real purpose of the work. It can quickly lose all meaning.

Personally I think the most chill-but-rewarding vibes are internal at mid-sized companies where software is integral to the business but not the primary business of the company. The "meaning" is decent, you can be closely connected to the people getting value from the software. There's broader HR and company culture but you're out of the spotlight of it, off to the side a little bit. You get to use all your skills and there may be new ideas you can bring. The team should be big enough that things don't explode if you take a vacation but small enough that you can see your work still matters. You might have to move to find it, though.

Seriously though, I can't find anything remotely non-tech without taking making at most 1/3 of what I make in tech. Seppuku might be on the table if I didn't have children.