I understand what you are saying but part of security is making it easy enough that people will use it, but hard enough it isn't easy to break for bad actors. People are lazy in general, if you tell 25 engineers at a startup they have to use two different tools just too handle credentials, the compliance rate of using 2fa will drop to nil, making accounts easier to hack. Don't get me wrong, it isn't like 2fa is so secure, it has been shown to be hackable for sure, especially when using SMS devices; but if done properly it can add a level of extra effort for a bad guy and if that extra effort is easy for engineers to use they'll do it. 1Password makes it this way.
From a corporate standpoint, I don't want people using their personal devices for SMS OTP (2fa) because then if they leave, are disgruntled or get tragically hit by a bus I am locked out of a potentially important service/account. I had this happen on three accounts in the past year where one took me 3 days to recover the ability to access it, another I never could recover and we had to work around it and a third that was absolutely critical but took close to two weeks all said (lots of waiting). That is insane, and all because people used their own personal devices (or similar) for SMS 2fa.
There are other devices you can use, and some enterprises do use hardware keys in addition to the password which works well and the more sensitive the system the more inconvenience people will tolerate and understand.
For me it boils down to 1Password works good for a reasonable price which helps startups and small companies. I also don't think using 1Password is just a tool and you still need a good password refresh cycle and to stop reuse etc. This way if a backup at 1Password was somehow compromised or stored improperly at your company or at 1Password at least you'd be insulated better.
It definitely does provide a single point of access that if compromised in a way which bypasses all their security a lot of companies will be hurting.