I've always been of the mindset that storing your 2fa next to your passwords at least partially defeats the purpose of 2fa.
The two types of attacks I worry about would be a hacked/leaked password from a third party site, or your password manager being compromised. While the latter is far less likely, it is still something I'd like to protect myself from as much as possible.
If my password manager is compromised, I'm well and truly fucked. If one site has shitty security (odds of which are approximately 1), having 2FA might help.
This shouldn't be the case. Using password manager shouldn't mean you only have one password, it should mean you have less password to remember. I use password manager for all the insignificant pages/apps like lemmy, strava, netflix, spotify. If someone hacks them they can cancel my subscription and that's about it. I don't store password for my email, bank or amazon in my password manager.