Yes, it's a single point of failure (probably more, depending on how you choose to define them) but it is invariably more secure than me remembering my super-nifty password algorithm.
It's not perfect, but I trivially generate very long passwords for every service, and have to remember the master password only of my email and my 1password account.
If anything is truly important, it will have 2 factor authentication.
If someone has access to my unlocked physical machine and an unlocked 1password UI, I'm screwed. Additionally, they could use the wrench approach [0] to gain my credentials.
This is not a use-case I'm actively trying to prevent. Nor is protection against state-level actors targeting me in particular.
Further benefit of 1password: my wife and I both use certain shared logins to access things like credit card accounts.
Instead of me having to get her on board with my password book, or special algorithm, I can just move a login into our shared password vault.
I suspect most people reading this are in a similar boat - we're more than happy to pay a few dollars to hire millions of dollars of specialized security knowledge to outsource this problem for us.
This is just too mundane a solution for most people to comment on.
Long live 1Password!