That's why the article says "verify, not validate". Send an email, have a process for them to confirm they received it.
If the user gets the email and completes the validation, the email is valid. If they fucked up, they don't get the email and the account never gets created.
No one ever gets prevented from creating an account with a legitimate email address, as opposed to "opinionated validation" where that absolutely will happen. Speaking from years of experience having a .info domain which isn't even all that odd, and at one point using gmail-style + addresses regularly. "Opinionated validation" has forced me to use my .com domain without a plus dozens of times.
I know part of this is intentional, those who know they plan to sell your email addresses don't want you to use the plus addresses, but that doesn't make the advice to not filter addresses any less correct.
While I’m opposed to opinionated validation as well, you seem to be missing the issue it tries to solve, which is the user mistyping their email address, not receiving the verification email, and either thinking everything is fine, or thinking that the process is borked, and in any case not proceeding and not becoming your customer. The goal of opinionated validation is to inform the user about an incorrect email address immediately when they are entering it, so they can correct it right away.
You could do soft validation that provides protection for common mistakes while still allowing users to use domains you didn't expect.
"Did you mean layer8@gmail.com instead of layer8@gmailc0m [Y][N]".