On your second point, not even entirely new games could do much to sell Wii U hardware, so more remasters would have hardly made any difference.
On your third point which ties into your fourth, the amount of ports, remasters and remakes has grown over time. The evergrowing game development times have made it financially more responsible to give old games new life because smaller teams could make them in a shorter time than entirely new games. We've been heading into this direction for about two decades, so the Wii U's failure isn't really important. Even if it had been successful, Nintendo would have moved over games to Switch to pad out their release schedule. People should expect the same to happen to the Switch successor, even if the new console is backwards compatible. In this day and age it's neither feasible nor realistic to forego the making of ports, remasters and remakes while having a robust release schedule at the same time.