You don’t have to agree for me to know I’m 100%, not 50
Excellent question.
Effect loops have never improved any effect that wasn’t specifically made for the loop (none of mine are), but they have made many sound way worse.
Blended signals were needed back when all you could get were guitar distortion pedals with no low end, but now they have actual pedals designed for it. And I don’t like how blends often make them sound like two separate signals. I’ve seen it referred to as bees in the background. Pretty accurate, I’d say.