[kevingadd]

You seem to have an unnecessarily narrow view of games and how they're constructed.

Try out Mark of the Ninja and tell me they were 'just trying to make an FPS'.

Picking an appropriate perspective for a game involves a lot of tradeoffs. While certain mechanics are most appropriate for certain perspectives (top-down 2d, isometric, first-person 3d...) a general approach to 'visibility' is not one of them. Visibility (or an approximation of it) applies to AI in almost every action game type, regardless of perspective. Whether they can see you or not is an essential consideration for creating convincing enemies, and AI allies need to know whether they can see foes.

You can also extensively use vision cone mechanics without having anything to do with an FPS. Classic games of the Rogue variety (i.e. nethack, angband...) all leverage vision cones and line-of-sight despite the fact that they predated 3D games of any kind.

[ANTSANTS]

I hang out in some indie/amateur game dev communities and it's like everyone and their dog is making a top-down stealth shooter with the exact same effect, the exact same mechanics, and the exact same "FPS in 2D" feeling. That's what I'm tired of, not 2D raycasted lighting/shadows in general (yes, I thought of Nethack while writing the grandparent comment).