I think you haven't any right to decretate if something is useful in general :)

For example a similar app, for me, is useful because I can split the money context from the login one. Then a login only app has less code, so less attack surface and can be audited easier. As said can extend the login record with useful data (for example alternative method access, a login history, etc.) that you hardly find in a standard wallet.

It's wonderful if you are happy with your LNbits instance, perhaps someone else could prefer a simpler/different/specialized solution. The market chooses, right?

Criticism doesn't mean is automatically useful.

PS: You forgot to reply about the server matter