You lose the Google content , since the export is lossy (docs , sheets, slides , etc) . And most of the value is collaborative . You’ll lose anything that you contribute to that’s not in your account . You’ll lose credentials (eg sso to third parties ), messaging access .

You’ll lose indexing and metadata , like Google Drive search , Google Photos search , thumbnails .

It’s a myth to assume the value is in the backup. Most of the value you have is in the access and the application

I don't have anything serious on Google drive, just some files I share with third parties that primarily exist on my network; and certainly no photos. Photos are on my NAS which is backed up on several disks; I publish them on a small app that I built, self-hosted (after years with Smugmug I left them two years ago).

Most accounts with third parties use domains I own that are not on Google in any way. Some still use a gmail address and I need to migrate those. But nothing essential.