Lol? Stealth is affected by light actually. Like I said, they overtuned it at release for the casuals. You can ramp up how light affects it using skytweak. Seriously, don't talk if you're not informed.
Factors that Skyrim uses:
Audio Detection-Non-directional
Audio Detection-Line of Sight(you see a moving target easier within your vision cone)
Visual Detection-Line of Sight
Vision Cone Radius
Light Level Magnitude(nerfed into the ground at base value)
Base Stealth Rating
Stealth Rating Skill Multiplier
Search Duration(the rate if they catch you out of the corner of their eye but haven't taken damage or verified your presence)
Search Duration-Detected(the rate if you hit them or they fully detect you)
Additionally, while it's not a value that can be adjusted, their base AI will go to your last assumed location to find you, then fan out and search randomly after that.
So in practice, there's a circle radius audio detection around them, a higher magnitude "audio" cone within their line of sight, their actual line of sight cone. You can tweak all of this including making light levels actually matter. Actually there's some other minor variables which I dunno why they did them that way, but that's the simplified version of what actually matters.
My preferred tweaks are to jack up how much light affects detection, increase the BASE stealth rate by a good chunk, then LOWER the stealth scaling per level significantly(better at low levels, much worse at high levels), lower the audio detection outside of the vision cone, then jack up visual within cone a bit, and audio within cone a lot more(since audio in the cone double as "motion" sensing i.e. seeing you move in the shadows. After that I make the detection out of combat like 1.5x longer, then take the combat detection and jack it up to like 2 minutes so once you're in combat you can't just hide for 5 seconds and you're done. If they catch a glimpse of you they think they're "jumping at shadows", but if they take an arrow or see you stealth it's time to fight.
This does mean you can do some sneak attacks after combat starts, but only until they catch up with you, or if you can snipe from VERY long range and relocate before they find you. But the jacked up "motion" detection in cone makes this a lot harder(and more rewarding).
So yeah. Skyrim's stealth code is good. They just prenerfed all their variables for casuals. Fix those and the game works great.
And if you want a good stealth game go play Mark of the Ninja or Invisible Inc. Dishonored was crap. I have no idea how it got GOTY. Also, I know it might be frowned upon, but I really enjoyed Human Revolution's stealth mechanics. The AI had the best "search" pattern I've ever seen. They checked vents and shit. Sadly they didn't group up so it made it trivial to pick them off. I want a game where enemies have intelligent search patterns but actually stick together. That would be awesome. Anyways, done with my little aside.