I don't think anything about lighting or battery availability is stupid, was just enough of it even on the first playthrough.
it's not merely about being able to finish the demo.
right now being out of batteries is a straight game over with no come back (unless you want to boost gamma like hell, or click each dark area randomly) for the detective route (boy route is ok because you can see the wall/door in the dark making it at least playable).
once the game get longer and puzzle harder, the strat will be -> waste your batteries once while figuring out what to do, then reload last save to do it with less batteries otherwise you might be game over 5h down the line because of those 'wasted' batteries (unless the futur of the game is simply clic the '?' with no puzzle or anything involved).
either make the detective route at least as bright as boy's route so that you can move around in the dark and only use light when you think you might miss something, or maybe make it that when flashlight is out of battery you can only see 1/2 tile in from instead of the usual 5/6, or have it slowly recharge when not in use (allan wake style). as of now, you could as well setup a timer ticking down "this demo will self destruct in 5min".
it's not even as stressfull as RE1 limited save because those have you chose how much of a risk you want to take when saving/going without saving. but here you have no choice but to use the light otherwise you can't even move forward so it come down to 'how fast can you find the random stuff on the map' (or more like remember where they are from your previous attempt), and if you can't, well, restart.