Yes, nobody forces you to buy them again.
And it's not like Nintendo is porting Wii U games instead of making new ones.
I don't think you realise how much work porting requires. If you look at the amount of ports coming to Wii U Deluxe... I mean Nintendo Switch my bad, then you can certainly say it sacrifices significant time and manpower for new high quality games. Even if you never had a Wii U, just buy one and get all the games without any obvious downgrades and at a much cheaper price and a much bigger library.