The reality is that a lot of the people in these threads have some really high standard for what they think action gameplay should be and when confronted with what game they actually enjoy they either dodge the question or they say it then quickly get their shit pushed in by contradictory statements about what they want.

If you like to combofag, play DMC
If you like score hunting, play Bayo or TW101
If you like mobile combat, play Ninja Gaiden
If you like closer melee combat, play God Hand
If you like parry focus, play MGR

The genre is hard to define because the only thing connecting these games together is being able to juggle regular enemies and having some form of cancel mechanics.

It's not about combos because not all games have in-depth combos. Ninja Gaiden can use launcher > izuna drop but the depth stops there, anything else you can do is overkill and not necessary.
It's not about scoring mechanics because Ninja Gaiden and God Hand don't have real scoring systems that anyone cares about and lets be honest, DMC's style meter is overrated and very easy to keep up. Not to mention that very few people actually try to achieve S ranks or equivalent for most of these games and it's just posers
It's not about hard combat because if you ignore score, a lot of these games can be beaten without too much effort. If you include score, there's a lot of score guides for these games that give simple strategies which rarely require any advanced tech

So what's left? What ties them together? Even if we use the criteria I mentioned, what's stopping god of war from being in this genre? GoW 3 has combos and cancels. My argument isn't that god of war should be included but that people in these threads have strict requirements on what games should be included when what ties them together is very loose ultimately. Time to stop "gatekeeping" when the reality is most people in this thread are here because they think liking action games makes them "better" than others