You seem very big on presumption but very light on reality. Let me give you some.

At various times throughout the 44 years that you quote, most major car manufacturers have participated in the WRC. Now, today, most don't.
Whenever they have ceased to participate, or not begun to do so at all, it is usually due to economic reasons.
Ours is a costly sport and the largest cost, as with any global activity, is logistics ... travel and transportation.
Indeed the reason touted for the promoters shying away from reinstating RNZ is that the manufacturers consider the event too costly to attend.

Now the facts are that New Zealand is no more costly to freight into than Australia or Argentina. It may be marginally, but not astronomically, more expensive to fly the crew there. Certainly not sufficient to rule out the event. So does this really mean that manufacturers view all far away events as unjustifiably costly?
And if that is the case, given that some of the current manufacturers are suggested to have limitless budgets, how much of a deterrent are these costs to others entering the contest?
Would there be more manufacturers if the costs were less? Would there be more opportunities for drivers?

My points have nothing to do with rally-cross or circuit racing or gymkhanas in car parks.
The fact is as soon as you put something in the air or on the water it becomes expensive.
I’d much rather see a dozen events well supported by a variety of manufacturers, and with more top drivers, than a skeleton of a championship with barely a handful of teams and no career opportunities.