And you can't convert your account to a regular Google account. I really want to untangle all this, but there's no way to (for example) export your Google Photos sharing settings and import them into a new account. I have hundreds of GPhotos albums, with many of them shared with various people, and if I migrate to a new, regular Google account, I'll have to manually set up all those sharing settings again. And this is just one of many difficulties; I'm assuming I'll also lose all my Hangouts/Chat history as well, with no ability to import the old history.
But I'll be doing all this sometime soon, as Google has decided to finally pull the rug out from under those of us who signed up for GSuite when it was free (well, "Google Apps for Your Domain", as it was known back then), and will start charging later this year.
This is all incredibly frustrating, and the level of lock-in is pretty severe after more than a decade of having this account. If I could do it all over again, knowing what I know now, I would have created a Google account without GMail[0], using my email on my custom domain, and hosted my mail somewhere else. Though, admittedly, back when GMail was first a thing, webmail otherwise universally sucked.