Wouldn't it make more sense to have a dedicated caldav/carddav only account instead?

I don't think so.

An account groups identity + a bunch of resources to get to all your data and acts as a logical unit for that.
The idea of the generic account would be that you can set up an account with whatever protocols you see fit.
If we had separate caldav/carddav accounts then there wouldn't be any grouping of those resources, so we i.e. couldn't automatically figure out how to send an invitation from the calendar.

If separation is indeed wanted you could still setup one account with only imap, and one account with only caldav/carddav.

So I'm essentially proposing that we have one generic account with all protocols we support that you can mix and match, and otherwise only service specific accounts that do the configuration automatically (so imap and maildir would go out the window as standalone accounts).

FWIW, the most important usecase I want to enable is kube with addressbook and calendar for anyone not using kolabnow.

I'm preparing the generic account already, but if you disagree about the approach, please let me know.

No. That's fine.
Let's try the "generic account" route.