I think it’s got to the point where the drivers title is important to the drivers themselves and to the fans, but the manufacturers can probably get a bit more mileage out of the manufacturer’s championship, in terms of marketing....but only in some countries. i.e. Ogier winning is a massive deal in France (to the general public), but not the UK, but Citroen may get more out of marketing that they are WMCs to the general UK public than if Ogier wins a title.
I think this is an evolving change we are seeing and it certainly contrasts the worth of a Driver’s championship back in the days of McRae etc.
I guess either way though, a manufacturer still gets to claim ‘we are world rally champions’ whether they have won a WDC or a WMC.... and that’s probably good for manufacturer involvement as two teams can potentily get bragging rights.