Lnbits sits on top of a lightning node. So it is not a replacement. (But they don't have to run on the same instance.)
And it has wallet management capabilities and also you can install moduls created by others to increase the functionalities of your lnbits node.
Here is an lnbits instance that is hosted by someone else:
Create a wallet and play around with it to get a good feeling. I think it is a nice idea.