It only takes like 40hp to drive a modern car at 60mph while it’s max output is many times that number.
So for the majority of its life a car engine runs at a fraction of what it’s rated for.
In my illustrious career I’ve managed the get the check engine light on twice by spirited driving….in rental cars.
As mentioned before the light airplane market is a mere fraction of the automobile market.
As far as cars keep in mind that a manufacturer often uses an existing engine with some slight modifications or some additional electronic jangles installed.
Point being even in the automobile industry they don’t design a new engine for every new model car and they can recoup R&D cost over literally hundreds of thousands of units if not millions.
There are some “new” aviation engine designs available, even for the retrofit market.
But it’s hard to justify a $70k engine installation on what is a $40k used airplane.
New airplanes even simple ones are eyewateringly expensive even with a prehistoric engine.
Let alone the recertification proces to now install a new engine design.