I feel like it's a mistake to consider mobile games as being part of the same market as PC/console games.
Sure they're both "games" but I don't know that they're competing for the same set of users - either people play one or the other, or the people that do crossover in both markets are probably playing PC/console games at home and mobile games on the bus or train.
And what about actual game sales and revenue through things like GamePass. It doesn't help your game if a million people bought a Nintendo Switch if 80% of them only buy Pokémon, Mario Kart and Zelda.
Pretty sure they already succeeded. Wasting effort supporting an advertising platform like windows is irrelevant to whether or not they successfully made a lock-free game engine.
Regardless of your feelings on the status quo, there is one thing you must do when building a game engine if you want it to succeed: support Windows.