Then it would be nice if Apple simply supported your preferred email address wholeheartedly and didn't keep trying to always rope you into an icloud email. Seriously, those are dark patterns that people hated (and still hate) about Microsoft and Windows.
I'm not sure if you'll find that helpful, but you can create a Google account with a non-gmail email. When you create your account, below the username textbox is a blue "I prefer to use my current email address". Never tried it myself though..
They've changed it now so if you want to signup for a Google account it asks for your existing email and has a text link to signup for a gmail. If you are on the gmail landing page and hit sign up then it's how you stated though.
It may well be that Google is worse, but I keep on having to opt-in my accustomed email address and shut off the icloud one. I've probably shut that thing off in Facetime over a dozen times. It keeps on coming back like some sort of boss zombie. It has even caused arguments with a girlfriend, when emails got sent to the icloud address because it keeps coming back. (Now forwarded.)
If you also have an associated Gmail account it won't let you use another email address as the primary one.
That said I'm in some apple limbo land where I need to switch to an email address for iCloud but it won't let me use mine since I had a pre-email appleID. Yay.
Still, you can meet someone organically and follow up with talking to them the next day knowing just their name and what mutual friends you have. Email and phone numbers are both unnatural arbitrary strings compared to names.
