The games market in general has grown exponentially. Most play action games or "RPG's" like Assassins Creed though, so, I'm very doubtful that the percentual amount of people playing "immersive sims" (I don't like that genre designation at all, it says nothing about the kind of game really) is higher than it used to be. Steamspy for Deathloop (which is probably the best to compare as it wasn't sold for peanuts yet) says 500.000 to 1.000.000 owners, which sounds high, but, if you compare it to the really popular games, it's a fraction. IIRC, Dishonored 2 was lower at that point, which makes me think that Deathloop is more popular because it's a more modern setting with guns in it.
By the way, you may know the game Myst. It used to be the most popular game world wide. Could you imagine that game being the most popular these days? The market has changed, people have changed. To be fair though, one has to say that video games used to be something for nerds, while the market has vastly opened up, of course, with especially console gamers making a big part of the market nowadays.