It's not so bad actually.
The Google Drive files are exported as you would expect and you can just copy them into some other sync folder as is. Takeout transforms any Google Docs and Sheets into Word and Excel formats (configurable), so you don't end up with links into your disabled Google account (contrary to how their Backup and Sync client works).
Emails are exported as mbox files, calendars in ics format. It's pretty easy to import everything using widely available email and calendar clients. It's also pretty easy to put it all back into another Google account, but you're right, it's not as simple as importing the entire takeout zip file in one piece.
What I haven't tried is what happens to files that were shared with you. I would expect that they don't get exported because it's someone else's data after all.
I think if the purpose is to let you move all your data to a different provider and avoid any lock-in, then Google Takeout is an honest and practical solution.
It's clearly not meant as a routine backup solution though.