1. It can only make 2D Mario Levels
I actually think this is why it will sale and do very well. It is great that it only makes those types, because everything can be polished. If it went into 3D it would need a totally different engine. You will have to start messing with cameras and such, it just wouldn't be user friendly, especially for the younger fans. I wouldn't mind a designer like that, Nintendo doesn't need to waste its resources like that on a Wii U game. Again, this is the selling point, and it really depends on how creative you can be.
2. Console based creation games have less longevity than PC ones
Depends. There hasn't been too many GOOD creation games that hit the market. Minecraft was definitely the biggest one, and it was because of the marketing and the way you can share with each other. This is where Nintendo is either going to do good or shoot themselves in the foot. If they start pulling Youtube videos for example, top Youtubers won't want to play it, and thus the marketing that they would have done would be hurt. Also, the longevity depends on the system as well. We all know the Wii U is going to die out soon. However, if this game will be backwards compatible to the NX, then they can continue getting the success and of course the DLC that you know will be added to this game.
The key to this game, is Nintendo needs to be able to make sure people can share. They need to have the good levels come up in searches.
3. Time released secrets are, always were, and always will be a BAD idea
Yeah, I don't like this either. It is there way of teaching people slowly. However, there should be an option to skip it. That's my opinion, but it is Nintendo. With every great decision they always have 3 more head scratchers. But it is not a make or break thing.
4. The Amiibo paywall content doesn't help, either.
Amiibo is a money grab. There is no other way of saying it. There is no hiding that. They wouldn't be 12 dollars a pop if it wasn't. If you don't want it, don't buy it. For example, I have yet to buy an Amiibo.