I don't know what your players do/don't find engaging, and wasn't wanting to talk about that.I'm not looking to rebuild the Tomb of Horrors, but sometimes my players will have more fun if I'm not holding back. Would they ask me to not hold back? I doubt it, they want to succeed, but they know I sometimes just unleash, and those can be some of the best fights and challenges they overcome. And sometimes that means catching them off guard, not telegraphing something.
I'm not blaming the fiction, of course I am creating it. But, why is that fact being used to tell me I'm doing it wrong? That I should change the fiction to fit with someone else's style, because their style is better, because the only reason I'm saying something is impossible is because I determined it was impossible, and that is a bad thing?
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I imagined the villain, then looked at how they would obfuscate their traps, because it is what they would do. I didn't decide the traps were undetectable then create my villain.
I'm saying that I don't think it's a good reason for saying I don't telegraph traps that the villain you've thought up would hide those traps. Rather, the question is how does it make the game engaging by having a villain who hides traps. If there's a good answer to that question then by all means devise that villain! But it's that question of what game elements will engage the players that (in my view) should come first.