Many years ago I wrote about the evils of microstock (here and here) and nothing has happened in that time to change my mind. No photographer should ever work for microstock agencies.
I do use a couple of traditional stock agencies nowadays, specifically Alamy and Rex, to send out editorial photos. I’ve seen some success with it. We’re not talking big bucks, but they’ve certainly earned me a modest amount of money that I wouldn’t otherwise have made. So, despite a few grumbles, I continue to use them.