I agree the game should have online player and would be more enjoyable if it was included. Still you should have done your research before buying the game. I had a similar situation with Overcooked on PS4. I was about to buy so I could play online co-op with my friend. Luckily I looked into the game before completing the purchase and realized it does not have online mutiplayer, only couch co-op.
New Super Mario Deluxe U was my first Switch game. I paid around $35 for through Amazon with a discount. The game is not amazing or anything but it is enjoyable. I think it works in short bursts in handheld mode. I think you should give the game a chance at least since you already paid for it. This is also why I buy my Switch games physically. (Next gen all my PS5 games will be digital.)
http://www.youtube.com/watch?v=F1gWECYYOSo
Please Watch/Share this video so it gets shown in Hollywood.
