Somewhere deep down in this situation there's the opposition of old-school and new-school mentality, and it's really surfacing probably because Temple of Elemental Evil was originally an old-school module but you're playing it (I assume) with some new-school rules - and more importantly, with some new-school mindset.

See, old-school dungeon delving, even in very large dungeons that required careful exploration, always supported a get in - get the objective - get out mentality. Your resources were constantly diminishing - food, torches, potions, spells and the like were running out.
Also, dungeons were dynamic, which, in its simplest form, manifested in wandering monsters. If you were methodically charting every single room and searching every corridor, you'd explore, say, only 8 rooms between random encounters on average; while if you were moving on fast, you'd explore 16 or more, and therefore had a much better chance of getting to the real good loot (and/or the real tough enemies) before wandering monsters whittled you down.
Add to this that the XP system awarded avoiding unnecessary combat and staying focused. You got more XP from large treasure hauls then from killing stuff, and in fact unnecessary combat probably cost more in terms of resources than it raked in in terms of XP.
And finally, old-school D&D didn't cultivate the notion of "guaranteed fairness" new-school seems to be so hung up on. There was always the chance of running into something really damn hard, and the more rooms you explored that weren't relevant to the Big Haul, the higher the chance was for such an encounter. The fact that your party had an average level of 5 didn't ensure that you'll only ever encounter low-to-middle enemies and in quantities that didn't threaten to overwhelm you. It was much more realistic, in a way: if there's a dragon or a mummy commanding an army of the dead residing in that place, what reason would they have for playing sportsmanlike? Nothing, if you were careless or unlucky and ran into them, you'd probably go down hard (unless you ran).

All this required a different set of player skills to thrive, skills which were, in a sense, much more 'realistic' than in modern editions. It was all about on-the-fly decision making, lateral thinking, and such tactical skills that are, at their heart, reminiscent of modern-day military tactics (appropriately, since D&D evolved from wargames).

But to get back to the original thought, one factor in the issue might be that you're playing with a new-school mentality which is really jarring to the DM who might have experience (and therefore expectations) with the original Temple.