You are fundamentally correct: to make your passwords safe from hackers you are making them harder for yourself to access (in this case by requiring MFA). Accessing your passwords now requires having access to a device (your second factor).
There are recovery mechanisms that you can set up ahead of time (a series of recovery codes for example), but for the most part I would agree with your premise: you will have a very hard time accessing your accounts if you ever lose your primary devices. For me the security benefit is worth the inconvenience.