I agree. I must have wasted weeks of my life trying to get access to systems that just would not tell me what went wrong. Often just returning a 400 error code.

I agree. I must have wasted weeks of my life trying to get access to systems that just would not tell me what went wrong. Often just returning a 400 error code. Or given the "username or password incorrect" message even it not true. It is even worse when you are developing the client or trying to access a new server. It could be a wrong user name. Or I should have used my email instead of the user name or the other way around. or the password or it could be that the account is expired or an expired certificate or maybe some negotiation of encryption codecs failed or an URL is wrong. or maybe the server-side DB was down. once it turned out to be a REST API that stopped accepting single-quoted strings generated by a client. Then you click the "I forgot my password button" and nothing happens. You do not know if an email was sent. Or if an email was sent, to which email address is was sent. Or if it was stopped by a spam filter.