I'm actually shocked to see that there are people that want immersion breaking mechanical equations, functions and logic gates thrown into their face. I agree with what you are saying but the perfect ruleset for this already exists in 5e and what you are seeing is Larian having taken liberties with the system, chosen to not implement it for whatever reason, or actively wants the presentation of their game to include these artificial arcade game features for whatever reason.
In 5e passive perception doesn't automatically trigger situations. It happens in the background. It affects the initial description of the area once you enter it and any desire for details ot a more detailed analysis requires you to roll. This works in tandem with the investigation feature. That being said, I do think that elements such as the level for a secret passage should only be seen prior to rolling one of these active checks if the main character meets the perception check. If a companion meets it they should hint for you that there is something worth investigating to prompt this check. The purpose of this is two fold as it would not only put all the power in the players hands but would keep your companions useful in a very realistic and immersive way. This feature can be improved if your relation status with them affects this to the point where they will keep it hidden from you or even tell you outright where it is which would even add a great deal of depth and significance to them.
That being said, traps and illusions include rules in regards to all of this. For traps passive perception would let you see the signs of traps(port holes, gaps in the seam in floot tiles etc) while figuring out what kind of track it is and how to avoid it requires an active check. As for illusions again passive perception will let you know immediately that something is wrong with a certain object but it still requires interaction to 'dispel' the illusion. In this case you do not need to roll anything but simply interact with the object to break the illusion.
This is not how things currently work in the game and I honestly haven't seen anyone make a convincing argument as for why they have deviated from this formula and these rules other than they are not aware of them, or consider their current system superior. In the case of the later it makes me question this full price EA and the point of giving feedback as it should be whichever system we as the players consider to be superior that should take precedent.
