Vents = more ways to navigate a level.
More ways to navigate a level = good.
Dunno the issue with them. Is the lack of realism of going through them?
It's that a completely insane, arbitrary thing that no one should ever expect to have to do, and no one would ever really think of doing, and would never actually work, is not only accepted without question in the context of games, it's
expected to the point of total nonchalance. Why isn't disguising yourself as an innocent chicken not a part of 60+% of all games? No one would stop to bother a chicken, so it's just a cool stealthy way to traverse levels. Everybody should be doing this all the time in games. That would make about as much sense and add just about the same interest to gameplay. Yet no chicken suits.