I think the key here is you have tried the other options, and importantly - you clearly know how to set those other services up if need be. For many if not most people, that would be entering the wild unknown.

Fair enough.

I have never understood using a gmail.com account for anything important.

It’s always been inexpensive enough to buy a domain and have an email address associated with it.

I also don’t understand startup founders who tie personal emails into a business email account.

Keep a separate email.

For one, a personal domain is less secure than a gmail.com domain. There have been quite a few targeted hacks, like Mat Honan or any number of crypto-holders, where a personal domain was socially engineered to be transferred to a new registrar (or password reset on existing registrar) where the attacker controls the MX records, thus your email, thus your password resets.

It’s much harder to transfer gmail.com, office.com, etc

That’s something I’ve been worried about since I switched to a custom domain email address that I point to another mail service: I protect my registrar account with 2fa, but I still think that the chances of someone hacking via social engineering my DNS registrar (Gandi) or the MX provider are much higher than someone hacking my 2fa personal @gmail.com account. I might just be paranoid.