I don't understand why we can't just let the market decide which businesses make sense based on their revenue vs. leasing the land. Presumably if car washes are so profitable it's because consumers want to use them, so why are we artificially restricting their expansion? It also provides a free subsidy to existing car washes who get to charge higher prices than they would in a competitive market. Restrictions to entering trade generally hurt consumers.
FWIW, I've used a paid car wash <10x in my life so it doesn't matter that much to me.
Someone opens a car wash in a central area. They self-declare a tax value for the land and its improvements.
We also allow that anyone can forcibly buy that land by paying that same self-declared tax value + X%. The sale can't be blocked.
We've ended the monopoly of land ownership, and imposed a free market on land purchasing.
Car washes that are a waste of the land they are placed on will get bought out and converted to other uses. If they are not, they will remain.
This, by the way, is very close to a land value tax, and all we've done is force a fair appraisal of potential value for a parcel, rather than the current, possibly underutilized value.
FWIW, I've used a paid car wash <10x in my life so it doesn't matter that much to me.