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.
WiiU has failed in many ways. The most important of them:
- bad marketing
- no strong exclusive title on start
- too much gaps in the release schedule
- too little third party support
- poor power to price
Good remasters would definitely help to fill the holes in the publishing window. Remember that one of the biggest premieres on the WiiU in the first year of life was Wind Waker HD. A few more such games and maybe the situation would not look so tragic and others would not start to withdraw from cooperation.
But you are probably right that we will see a lot of remasters on the Switch successor - in one form or another. Anyway, the music and film industry also often use old hits, because it significantly increases the guarantee of success.