I will never understand the thirst for tower defense, but I would point you in the direction of the multitude of them that exist on 3DS!
Honestly, I'm not sure what I'm craving for from the indie market on Switch. I suppose I've become quite fond of the "Adventure of Link" -a-like lately, with Elliot Quest, Shantae and the Pirate's Curse, and another indie title, Chronicles of Teddy, filling that niche (Chronicles of Teddy is an amazing game, I wouldn't recommend it on Wii U because of its severely bugged state). Some might liken Pirate's Curse a bit more to Metroidvania and I understand that, but disagree because of its largely straightforward and inorganic design. If they're anywhere near as fun as Elliot Quest, I'm down for them.
Honestly, I'd really just like to see interesting content on the eShop, something the Wii U eShop lacked severely in comparison with 3DS. The former had many enhanced versions of pre-existing games and a few timed exclusives, and then kind of devolved into a mess of ports, terrible, terrible things, and the rare gem. 3DS had the Guild01 and 02 titles which were unique and a high quality- this sort of paved the way for absolutely wacky sorts of games on the system, though many would also say the standout debuts by Wayforward, Renegade Kid, and Image and Form did the same thing. I just hope that sort of material exists on Switch- cheaper, but reasonably-priced indie experiments in form.