If you don't play games online...then yeah...you kinda don't need this service. It should go without saying.
Since I do play Smash online and have since Brawl, I need this service. The online games, deals, and cloud saves are just welcome additions to me.
I think the way they improve the service is since everyone likes voice chat...include system level voice chat for Nintendo games. Add different tiers of games. Anybody expecting SNES, N64 to be a part of a $20 are kind of insane. And improve their netcode. This is literally all that can be improved as far as an online service is concerned for the price.
Voice chat is a system level function that has no place in an online service. Experiencing lag in games is not solved by adding larer servers, it has to do with Nintendo's Netcode which isn't horrible, it just needs work. Every Nintendo game uses a dedicated server of some sort, implementing larger serves really won't fix disconnection issues or lag all that much. Messaging, again shouldn't be a part of an online service...this should be system level. The Wii U did all of these things without an online service being necessary. So some of the things we're asking for doesn't necessarily revolve around the online service and they shouldn't.
The deals...eh, yeah they suck so far. But Nintendo already gives you $3 for online purchases of $60 or more. $6 if you pre order their biggest games. And I think that's not bad. Adding any more discounts would be welcome but I highly doubt Nintendo would make this a part of the online deals. I don't think the service itself needs that much work compared to what the competition offers for 3X the price. They're close but there are few fatal flaws they're making to make it undesirable.