Personally, I consider “retro graphics” to specifically mean the graphics evoke the look of an old game system, as opposed to just having “lo-fi” art. So I’d say that Celeste has great pixel art, but it’s not retro graphics, since it doesn’t remind me of any old console’s look. In addition to the games others have mentioned, I’ll point out these ones.
Indie games using retro graphics is nothing new. The ratio of effort vs looks is pretty good. The solo dev of Cave Story (released 2004) said that was why he went for that aesthetic.
Steam input is absolutely baller. I use it extensively with my Steam Controller. For FPS games, I have gyro aim activate while the right pad is touched.