FWIW these do not sound very fun, at least for most people. Gamers tend to say that they want more complex systems but when games with complex systems come out

FWIW these do not sound very fun, at least for most people. Gamers tend to say that they want more complex systems but when games with complex systems come out most players either dislike them and/or go only for the most simple and straightforward approach while ignoring the rest (even if that approach isn't as fun as the more complex stuff). So most games tend to go for simple systems presented through enough smoke and mirrors to give the illusion of complexity. Also keep in mind that games aren't made in isolation, instead they have tropes that players are heavily relying on. A very common example is the "red barrel = explosive barrel" trope. That trope is mostly harmless in that if it doesn't apply (ie. the game has red barrels but they do not explode) then nothing bad happens. But what you are describing with blood trails sounds like the regular cosmetic blood decals almost every action game has that can be easily be missed by players. But note that i'm talking about the generic action game here, not a game designed explicitly around one of these mechanics - that is another matter since you expect it to be like that. But if these mechanics you mention are used like any other "secondary" mechanic in a game (and especially if it is a game that offers alternative approaches) then it'll fly over most people's heads and be ignored unless the game explicitly mentions it every single time. And this is normal, there is only so much you can keep in your head while playing (especially if you consider how long some of these kitchensink games are and how little time per day/week some people have). Hence simple mechanics, smoke and mirrors.