I think the main reason for much of the falling of road racing is the cost of the top tier tracks. Those facilities can get what they want and don’t have to work with clubs if they don’t want to. Because of these high costs, the clubs have to charge each entry more. Parking lot events and purpose built sprint tracks can absorb costs a lot better.
KART is a great group, but 4 of their 7 races are at parks where the rental is WAY less than the other tracks. This helps offset the top tier tracks. Not a dig against KART at all, they are making it work. SWRA had Oakhill to help offset costs, but when Oakhill went away and those promoters started losing big money, SWRA went away.
Not sure what the answer is except to try to model after KART, and get back to the roots of road racing.