I understand your concerns and I too would like to be able to explore old dungeons more tranquilly (hell, me and my friends would spend days RPing in Haukke Manor pretending it's the house we'll never afford XD), however there are a few things to take in consideration:

1: dungeons are on separated servers, and more than likely, the early ones are very limited. That's what the time limit is there for, you need to leave the instance to let another group go in. Maybe they aren't used much now, but it's how they were made and I don't think SE would modify them just for the sake of letting someone explore.

2: I don't think FATEs that "require some thinking" are the right thing for this game. Just think of FATEs as they are now. It's already almost impossible to get a bard with main aggro on the FATE NM to stop kiting so others can attack it too. "Damn those bards", some say, but why do bards do it? Because healers hardly spend any time healing in FATEs, favoring nuking with Cleric Stance, Holy and Stone II. "Damn those healers", some others say, but then there are tanks, who, fearing to not get healed, often times will not even try to lure the boss's attention.

Now imagine all these "mindset flaws" combined with a FATE that may require, I don't know, to place the boss in a specific spot (like the Facers in Qarn), or to interact with switches mid-fight (think of the Gil Turtle guildhest. I've had people in AF gear kill the turtle without even trying to read our cries to stop). As you can see, FATE is just the wrong activity to require 'elaborated strategies'. It's pretty much like Besieged in FFXI.