That is why you should add a custom domain. You have the same lockout issue with Outlook, ProtonMail, or any email service where you don't own the domain.
Yeah, the question is whether google makes sense as a mail provided once you've decided that you needed to pay because of that feature.
If you're a company and don't want to manually handle email provisioning? Sure, why not. If you're an individual, Google isn't great. You could have a decent feature set along with great customer support elsewhere.
I misunderstood you then, "having your mail on google and syncing them" sounds like you still have a @gmail.com but taking backups. Having your own domain is indeed the safest, I do that actually
If you're a company and don't want to manually handle email provisioning? Sure, why not. If you're an individual, Google isn't great. You could have a decent feature set along with great customer support elsewhere.