A lot of us are in tech and we come across these problems and just troubleshoot our way around them and don't really think about them, so I figured a "case study" might be helpful. ~~Image unrelated.~~
Anyway, yesterday I tried making an alt account on lemmy.world. When last we left the situation, I had been notified that my registration application had been denied, but I'd been asked to confirm my email and https://lemmy.world/u/sergio had been created. A couple helpful commenters suggested my account might still be under review.
- Today I tried logging in again. But when I entered my username and password, I got a popup that said "incorrect login credentials". Maybe I needed to verify my email again? I went to my email, clicked the "verify your email" link, and just got a page with text that said "verify email" and nothing else. Maybe it didn't like me using my username to log in? So I tried logging in with my EMAIL and my password, and still got that "incorrect login credentials".
- Maybe something's wrong with my password? I'm using a password manager but OK, let's just try changing my password. I clicked on the "forgot email" link on the login page. I entered my email address and clicked "reset password"... and nothing happens. No feedback, and I don't get an email. (10 minutes so far).
- maybe I should check https://lemmy.world/u/sergio ? Hey, that's no longer there, I just get an error! I check the user page of another lemmy.world user and it works, so it's not a server problem. Maybe my application really was denied? Was it really reviewed? What do I do now?
(my intuition is to try again with a different username, email address, computer, and browser from a different location at a different time of day...)

You're advising a technical solution to a technical person.
OP's not looking for a solution to his specific problem, he's showing that as a technical person he's faced with an issue he's unsure how to resolve - now imagine the average person facing this problem.
OP's right - the sign-up process is clumsy and problematic on any instance for the average user.
Yeah, maybe I should re-emphasize in the post that this is a "user experience" kind of post. Personally I have lots of hardware, OSes, and phones laying around (and an existing lemmy account!) so I'll figure it out eventually.
FWIW a lot of companies don't do user experience studies. Apple is famous for it, but even big places like Google and Microsoft often skip on this.
Yep the learning curve from logging in to finding communities took about 45 minutes or so for me.
I can see that being a turn off for many users