With no second factor you are vulnerable to anything that could sniff your password. I guess this is fine as long as you never log on from any untrusted machine/location?
Also any phishing you don't notice, or many browser hacks. A good 2fa (u2f, fido) authenticates you to the service, but also verifies the service is what you expect.
I'm rather averse to using cloud services for password management. KeePass all the way, syncing the key file with syncthing or something.