I know. That's just a disaster waiting to happen. "We got hacked." "You don't say ..."
For the first and last time:
ANYTHING on the internet is NOT secure
Use a local password manager.
Well, now that we have the word of someone that has absolutely no clue how infosec works I guess it's case closed right?
As far as how secure this service is... well... meh? Who the hell knows. Would I keep the launch codes there? No. My password for that Cartoon network? Sure. The point is, you seem to be claiming that your local hard drive is safer than a websevice literally dedicated to security. That's laughable to say the least. IF this site really is what it claims to be, then it's definitely more secure than your local hard drive, but certainly not as secure as simply memorizing the password.
The concern I would have immediately would be that you have to trust that vendor. Are they located in the US (or whichever country you live in so you can sue them) and subject to the jurisdiction of US courts should they turn out to be bad actors? And almost more importantly, do they keep all of their data on US servers? Being headquartered in the US but outsourcing your database to China would kind of defeat the purpose right?
When you get down to it, when you get into big-time security in major corporations, it's not really that you're jumping through lots of hoops to make sure the data is secure. You will ALWAYS fail at that. You just can't stay that on top of things. What you're really doing is trying to ensure that if there is a breach, you can recover from it and that you have someone to sue/blame to pay for the recovery. So you make sure you pick a service that's in the US, and is well insured. Then you leave it up to them and their insurance company to duke out the difference between higher premiums or more security people.
But if you're just Joe-schmo at home, and you want to store credentials to your netflix accounts and such? And it's a huge well know company like lastpass? Yes, they are more secure than your windows harddrive. A lot more secure. Maybe keep your bank login on a post-it note in the back of your sock drawer just to be safe though.