Paying 3rd parties wouldn't realy fix anything.
Assuming that 3rd parties would be ok with allocating staff to a project seen as having a low proft margin, 99% of MS and Sony fans just would buy one of the other versions.
Also, money spent on ports would probably mean less exclusives for Nintendo, making Wii U less attractive as a standalone console or companion to PS4 or XB1.
It's true that Nintendo failed.
They wasted too much time with getting steady release schedule (2015 is the best they will ever do) and now they are approaching that time where development for the next gen has to start, leaving less teams for Wii U games in the future.
It didn't help that Nintendo made too many mistakes and the intended audience that they truly marketed the console for since day one, neither cared or understood what it was.
After that it was just a slow collapse of their strategy for Wii U.
Delaying sucks but doesn't really change anything.
