Bad Stealth
Not every game needs a stealth section. Really, I know this is a shocking revelation. But not every game even has mechanics necessary to make a stealth section fun. So, unless your game is designed around being a sneaky dude, don’t do it. If your game is about shooting guys in the face, then that’s that. Don’t get cocky and insert a stealth section ¾ths of the way in. And even if you do, do not, do not have me “die” if I fail to stealth (and extra anger points if stealth fail means death and I have to sit through a cutscene again!). But really this is not just stealth.
Basically, every game has a main mode of operations, a cruise altitude, at which it is good, which it is designed for. Stray from that place too far mechanically, and things start falling apart. This works in reverse to stealth as well. If you build a sneaking game, don’t suddenly turn it into an all out shooter. Don’t try to do things with your game mechanics that you didn’t design them for initially. It is. Not. That. Hard.