2FA isn't limited to one device, or specific 2FA mobile apps. For example I use oathtool for most 2FA things; you just need to store the secret (often in the form of a QR code, but many services will also offer a text version, and if not you can decode the QR).
100% reliance on a phone which is easily lost, broken, stolen, etc. without backup is really bad IMO. My bank (Revolut) only had a mobile app, and no way to contact them outside of it (I tried...) I need to switch banks.