And now I'm trapped in this multi-app universe where every entity uses a different app. My employer uses Symantec, my school uses Duo, my bank has its own app (as does Steam), and a handful of sites use TOTP.

Argh.

At least TOTP (and U2F) are standards. All sites and organizations should be using them, not something they've created themselves.

DUO and other similar tools where you accept on the phone instead of getting a code and having to type it in can be more convenient than typing; and provided you get the push, you can take care of it from the notification so you don't have to find the app, so it's not terrible if you need seven different apps.