You have blinded eyes and are looking just inside your little world. Many GM cars are very behind Toyota, Honda and others on design. Toyota will soon be the largest car manufacturer in the world, the customers obviously like Toyota's, Honda's, etc. designs and quality, because as you state they generally cost more, but the difference is much less than you suggest and is decreasing. Recently the big 3 have seen dropping sales, while Toyota, Honda, etc. have had steady sales increases. The customers are talking with their dollars.
For example one thing I definitely need in my cars is a full size matching spare. GM's recent designs (even of their smaller SUVs) don't have a wheel well capable of holding a full size spare, while most Toyotas actually include a matching full size spare.
GM has been trying to catch up in design in the last few years, but their cost structure is killing them. The income from GMAC and retained cash has been keeping GM above water. Those days are quickly ending.
Where do I stand on my car purchases? In the 50s I switched to imports being very unhappy with the 50s cars; back to big 3 cars in the 60s; back to imports in the 70s; have bought big 3 cars since 1979. Unfortunately I don't see a current big 3 car product that meets my requirements.
However most Toyotas, Hondas, etc. are no longer imports to NAFTA, so my choice of a non import is much larger than previously!