Despite how much Nintendo seems to struggle with anything new they have handled DLC really well for the most part in my opinion.

Mario Kart 8 I think was their first major foray into it and it gave us 16 new tracks, new racers, and color options for Yoshi and Shy Guy.

The DLC for both Hyrule Warriors and Legends added a TON of new content to the point that it's almost overwhelming to me (and I expect the same to happen again on the Switch).

Finally both DLC packs for Breath of the Wild were satisfying as well. It didn't feel as strong as the previous two examples, but I wasn't disappointed.

Red Dead Nightmare is another that I hear people praise as DLC done right, but I haven't played much into it (plus it was packaged with the game for me).