When I say "classic TV", what immediately comes to mind, and what falls into that ambiguous area where something's old, but not really classic?
I don't think that analogy works. TV and movies are very static and very well-defined mediums. We're still using techniques from the early 1900s to make most shows nowadays. If you watch Citizen Kane, the dramatic shots in the movie influence pretty much all modern visual media henceforth. What makes something classic is a settled science of how old it is and how much influence it had in addition to how popular a show or movie was.
With games, there's way more variability and differences in the mechanics of each genre of video game compared to movies/TV, in addition to being a much younger field that thrives on multiple different interpretations of fundamental axioms of how to make a fun game (depending on genre, platform,etc). But there are epochs of graphical/programming/design paradigms which are tied to each generation of gaming console and how the games they support. Atari 5200 games, SNES/Genesis games, PSX/N64/Saturn games. PS2/Xbox/Gamecube games and PS3/Xbox 360/Wii games have very noticeable graphical and design hallmarks that differentiate one generation from the next.
Ever since the 8th gen, with the PS4 and Xbox One, that's pretty much gone away as game design is pretty much an afterthought in most games and the focus is on graphics, which we are at the descending end of the diminishing returns curve. Add to that indie games kinda doing whatever (for better or for worse) and you really can't use retro to define old games since retro always meant that this has the hallmark of a particular era in gaming. When a game from 2014 plays the same as one from 2024 (assuming they are the same genre and everything like that is controlled for), that concept can't really be applied at all since nothings really changed in terms of the core game design.
Thus, it's easier to call games from the 7th gen and before retro since they have actual design and graphical differences that make them stick out as something from the past whereas in that list of games you posted in the OP, I think only Shovel Knight sorta counts as retro since it is inspired by NES platformers and it is something that has a lot of the design hallmarks of the first wave of indie games of the late 2000s/early 2010s like Cave Story, Braid, Limbo, They Bleed Pixels, etc. There might be others but if you played most of those games newly in 2024, you wouldn't get the impression that they are a decade old now.
Edit: Looking at the list again, I think Octodad and Goat Simulator count as a retro games just because they do kinda give off that same pre-Gamergate indie vibe. I'm not counting any of the other indies out just yet, but for certain the AAA/AA games aren't retro. Again, they all look or play just like most modern games today.
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