Rally5 Kit aims to be regional cup class. It doesn't really "parasite" on manufacturers as there is close to zero interest both from drivers, who rather choose Rally4, so I guess there is no reason to lobby against that. I haven't seen many Rally5s "in wild", most of them were in Toksport Clio Cup.

But don't forget that Rally5 Kits have to be homologated through ASNs, so there is still control over who can build a car.