Shmups had a huge comeback the last decade WTF are you on about? Something does not need to sell 1 million to be profitable. Those games are made on small budgets that even 500k for many of them is a massive success. Also Nier Automata sold 5 million and a chunk of that game is a Shmup directly inspired by Ikaruga.
In terms of relevance.
Arcade Racer. We have some good indies but no studio is willing to do a true 90s Arcade racing game.
8th gen lacked really fun fast paced TPS games like a new VanQuish or Binary Domain
*th gen lacked Armored Core. I love DXM but that's a more arcadey game. Which I prefer but still be nice to have a real AC game.