You can get grass to grow well in the shade.

No you can’t. Grass will put up with a lot; how any plants will put up with being regularly cut down and walked all over? Like everything it has its limits and it is never happy in shade, needing full sun to do well. What about shade “tolerant” grass seed varieties you say? Yes, some grass is more tolerant of shade than others; but that’s not the same as happy in shade. If the shade is slight these are probably a good idea, but once you start to get under trees and the like you cannot expect them to be any better than any other grass.