It is frankly ridiculous how unintuitive it was to add an email account to Mail on iOS. This is possibly the most basic functionality I would expect an email client to have. One would expect that they go to their list of mailboxes and add a new account.

No. You exit the mail app -> Go to settings -> apps -> scroll through a massive list (that you usually just use for notification settings btw) to go to mail -> mail accounts -> add new account.

Just a simple six-step process after you’ve already hunted for it in the mail app.