Just downloaded New Super Mario Bros U Deluxe and...Honestly, I have no idea why people dislike this game so much. It's as close to Super Mario World as Nintendo has ever gotten EVER, and while the levels aren't AS memorable as they are in Mario World, the level designs are all pretty damn good.
Easily my favourite 2D Mario game since Yoshi's Island. One of my all-time favourite Mario Games period, and while I do agree that full price for the game - even with the Luigi expansion - is too much, I have to say I love it. Plus, now that I don't have to play it with a sideways Wiimote, I like it even more!
Mostly because at the time of the original release people were sick of the "New" series and art style. It was the 4th in 6 years and only 3-4 months after the 3DS release. People wanted Nintendo to mix things up more.
It has more to do with people believing that the game sank the Wii U, much like Super Mario 3D World is disliked for the same reason. Then there's the group who has always been delusional with statements prior to Wii U's launch like "Pikmin 3 is the only system seller that Nintendo has announced so far," basically people who despise any 2D Mario.