I see your point, but the problem is that the tags will grow to be highly specific and the amount of tags required will explode. You have to keep in mind that developers are expected to include any tag relevant to their game.
Imagine a game like big brother. This game currently has 21 tags: 3dcg, anal, sex, bdsm, blackmail, corruption, drugs, female, domination, footjob, handjob, incest, lesbian, male domination, male protagonist, masturbation, milf, ntr, oral sex, romance, spanking, vaginal sex, voyeurism.
If we apply your idea, the tags would look something like this: 3dcg, anal (by player), sex (with player), sex (without player), bdsm (by player), bdsm (against player), blackmail (by player), blackmail (against player), corruption (by player), corruption (against player), drugs (to player), drugs (by player), female domination (against player), female domination (to others), footjob (to player), handjob (to player), incest (sister+sister), incest (brother+sister), incest (mother+son), incest (nephew+aunt), incest (aunt+niece), lesbian, male domination (by player), male protagonist, masturbation (by player), masturbation (by others), milf, ntr (by player), ntr (against player), oral sex (by player), oral sex (to player), romance, spanking (by player), spanking (against player), vaginal sex (with player), vaginal sex (without player), voyeurism (by player), voyeurism (by others).
These are the original tags, just changed to match what you are describing, to the best of my abilities, from what I recall from playing the game. You see the massive increase in tags? Nobody wants to read through all of that. Also, try to imagine the poor dev, who will have to remember every possible scenario his game offers, and watch half his game page occupied by tags.
I understand where you are coming from, but it is not realistic to practically incorperate it into the system.