That's exactly what happened with me. When people ask why I retired "so early" (I'm 56) my first answer is always that I did it because I could. I was fortunate to have accrued enough that I didn't have to keep doing something that had become more burdensome than satisfying, so I stopped.
As to why it had become more burdensome, some of the OP's points ring pretty true. Software development is much more rushed than it used to be, which is not at all to say it's more efficient or productive. Everybody wants to rush into coding without having a real anchored discussion about approaches and pitfalls, then rush into coding the next thing before all the really "interesting" bugs that live in the interstices between unit-testable components are dealt with. Yeah, I know the excuses, and I'm sure they'll be repeated in replies here. Basically they all come down to "don't worry we'll rewrite it next year anyway" which is not entirely wrong but I got tired of being disparaged for wanting to be even a tiny bit further on the "get it right the first time" side.
And then there's the ageism. Like other -isms it's never as simple as "I hate X" but more about failing to consider X. Open-plan offices are more problematic for older people because of hearing and personal-comfort issues. Mandatory oncall shifts are more burdensome for people with kids than those without. A senior developer trying to apply an idea learned on other systems will often be blocked because those systems are assumed to be irrelevant, but a junior developer reinventing the exact same idea in the context of the current system will get a bonus or promotion. To some extent it's just good old NIH, but when it consistently gives one group an advantage over another it's discrimination. "Only people who grew up in this environment can add value to it" is ageism.
A lot of these issues are much more prevalent at certain companies, notably FAANG, so arguably they could be improved by going elsewhere. Which would have meant going through another one or more BS interview processes for what was likely to be a slight improvement because everybody imitates FAANG. "I prefer not to" as Bartleby the scrivener famously said, and I suspect that's the same conclusion many other senior developers reach. We've made it so that development usually becomes more and more of a chore as people become more senior (no it didn't used to be that way), so we shouldn't be surprised when they take the earliest exit.