Thing is, it's not all about challenges.
A lot of the game involves non-challenging moments and activities - examples: talking to shopkeepers, travelling through previously-unseen parts of a safe realm, banter and discussion with other PCs, etc. - yet these still nicely fall under the pillars as currently defined (in order: social, exploration, and social).
To say something's not in a pillar unless it's presenting a capital-c Challenge seems...odd, somehow. And I wonder if that's causing some of the disconnect here: you (and maybe a few others) are trying to tie everything to challenges, where I (and, I think, some others) are not.
And this is relevant, in that the non-challenging portion of Exploration pillar activities will be higher than in the other two. Combat, by comparison, will have a very low non-challenge portion; with Social somewhere in between and more highly variable by table.
The reason Hussar is focusing only on challenges, and I think he is right to do so, is because that is the part of the discussion that matters most for the issues in the exploration pillar, and too many people are trying to have too broad of a view of “exploration” to be useful.
Is describing the majesty of Mount Crumpet part of exploration? Whether it is or isn’t, it would never be covered by the rules and it would be impossible to engage with. Describing a howling blizzard is easy, but when we describe it, set it up so that the players feel that going out tonight would be dangerous, but they do it anyways… we find that it isn’t dangerous. Per the rules as they are written, if they went out in winter clothes (a bare minimum that they should have) then traveling through a blizzard is just as challenging as traveling through a foggy morning by the coast.
And so, yes, there are non-challenges, and they can be important, but they are also things that are generally outside of the rules. And if there were strong ways to make challenges in Exploration without gutting the rules, it wouldn’t even be a question. But there aren’t, and since talking about “exploration in general” is getting confusing, then we need to focus in on the issue people are having. Which is explicitly exploration challenges.
It's the "automatic" part that bothers me, as so many things aren't automatic at all.
Realism, mostly. Using the "search the room" example, if I hide somethine really well in a room - say, in a very-hard-to-detect secret compartment in the floor - and I send 100 different people (or groups) in to search for it, even if they have all day the odds of all 100 groups coming out having found it are negligible. Ideally, if my hiding job is good enough none of them find it; but it's inevitable some will just by fluke and some others will by either skill or deduction or whatever.
But there also gets to be a point where the risks are nil and the chances of failure so low, that I don’t see the point in making failure a possibility. There have been times when my DM has the party split, and one group has to wait three hours in the guild hall to get a license or whatever, and my character is searching the victim’s home for clues. I’ll just tell the DM “I spend two hours searching every part of the room”
Is there a chance I missed something? Theoritically yes, but practically if searching a room takes 10 minutes, I could roll six times and take the best result, and we all know the odds that are incredibly low. And I know, you don’t like it that people don’t have to state every single place they look, in detail, but why take that table time for something that we both know I can do? Unless you are expecting me to mess up and forget something IRL, and I’m just not interested in having to constantly prove myself to get the clues. To me, it is just tedium.
And on the front of realism, what you just described is literally how they train law enforcement. Per 5e (and I know, the changes between editions) if you are proficient in a skill, you are considered good enough at it to have a job doing that skill. So, if you have someone trained in Investigation, they are just as good as law enforcement. Expertise might be the level needed to be playing in the spy-counterspy level. If you sent 100 spies trained in counter-espionage into a room where you hid something, even really well, and gave them all day to find it do you honestly think the majority of them wouldn’t?
You hid it in the floor? One of the things I’m doing is tapping, checking and running my hands along the entire floor, because people always hide something in the floor. Then I do it to the walls. Then I do it to the ceiling, then I door it to the door, and the wardrobe, and on and on and on.
Additionally, the more important you make the single roll, the more resources they will stack into that roll. They might fail a DC 20 when they have a +7 mod, but if they have +7, advantage, a +1d8 and a +1d4 the chances drop precipitously, and of course they are going to then do that for every single roll.