>Why are developers who work in an agile environment miserable? If you take scrum, doesn't it include retrospectives, with the express purpose of allowing developers to reflect on their misery and to gradually improve their condition?

first thing to improve, get rid of retrospectives

second thing to improve, if having retrospectives have them in such a way that nobody feels like they have to come up with some things you can improve, keep doing etc. etc. every two-three weeks.