[xyzzyz]

But that’s the entire point: the planes are using those museum piece engines purely because these are certified, and certifying new engines is an extremely hard, close to impossible proposition from business perspective. Sure, there is a way to work around the overly onerous (the mere fact that almost no new piston engines are getting certified is a clear proof that the requirements are excessive), but what would be great is if we simply could innovate in GA like we can in cars or boats or electric scooters.

[p_l]

Car engines, scooters, or marine engines don't have a tendency to kill user if they fail for any reason.

Also, the real reason there's almost no new piston engines is that there's no real demand. Especially since you need to certify the plane with the engine as well. Thus we face mostly incremental changes, because any single development won't bring enough demand to justify the changes. Meanwhile there's not enough money in the market to actually try banning the old engines unless you want to cripple a whole sector.