Hi Daniel Grabow,
Thanks for sharing updates with us.
It seems return back to the modern experience, click Exit classic experience in the bottom left corner of the page is missing. I have tested from my side when I go to setting> library settings>Advanced settings and under List experience click on Classic experience then I also cannot see switching button/option at the bottom left corner of SharePoint online page.
To view switch option, please try to go Library Settings> Click Advanced settings and then scroll down to List experience and Choose the new experience. Closing the browser, open the browser again and navigate back to the library to see the result.
For more details check Switch the default experience for lists or document libraries from new or classic
I appreciate your understanding and stay safe!!
Best regards
Waqas Muhammad