Automotive engineers view it as a problem but most drivers probably are unaffected by it in their lifetime. A passenger car's automatic transmission is generally just a bad choice of a device to immobilize a car's wheels. It is difficult to service and has other uses (namely: propel the vehicle) that are prioritized in the design. By contrast, wheel brakes are designed to be easily serviced and their design is centered around stopping the car.
When relying on the transmission for park, this engineering trade off results in the entire lateral force of the car resting on a tiny little piece of metal inside the transmission, that isn't designed to be constantly worn, the only thing keeping the car in place, easily replaced, etc.
There's also this aspect of - transmissions are mutable, they can go in a lot of different vehicles. You can have the same transmission in a 2000lb sports car and a 8000lb truck. How big should the parking pawl in that transmission be? How do you make that decision before you even know what vehicles the transmission will go into? What happens when your transmission that was originally designed for a 2000lb sports car ends up 20 years later in a 9,000lb truck towing a 3,500lb trailer? The parking pawl does not change.
Brakes will be serviced dozens of times over the lifetime of a vehicle, while the transmission might never be serviced. That's enough reason alone to leave the important task of immobilizing the car to the brakes, not the transmission, in my opinion.
