When I do root analysis, I look into internal logs, server metrics, recent source code changes, and related systems. I am sure this can be partially automated, but this is a lot of work.
An API monitor that can only tell me "You have elevated first-byte latency and increased 5xx rate" is pretty useless, and I certainly don't think it can offer me any "plain-english suggestion" for this problem. What is it going to tell me, "git gud and fix your servers"?