Addendum:
I've completed it a second time, attempting to do the content I didn't get around to (megadungeon and bounties).
It didn't take. Too much copy-paste in the megadungeon. The bounties started out fun, but midway into tier-two bounties I grew bored with the formula and gave up on those too. Funnily enough, the most memorable combat moment happened with the big ogre fight outside the ogre bounty cave: it was literally down to a near death ogre matron and a cowardly-kiting Grieving Mother. As fortune would have it, an elder stag happened upon the battle field, the ogre matron did something to piss it off, and it delivered the killing blow. That was some amazing, unexpected emergent gameplay right there.
I do recommend foregoing sidequests (excepting Raedric's Hold and possibly anything else that eventually gets cut off) and sticking with the critical path up until the point of no return. As I believe I've mentioned before, this is the ideal way to play if you're going to complete the White March, since you'll be just shy of level 7 by the end. However, I don't recommend going into Sun in Shadow at level 7 or even 8 (which is what I did). I managed well enough with the encounters leading up to it, but Thaos and his statues were a brick wall. With his practically-permanent Shields of the Faithful, my team had an accuracy of 0% against him and I lacked the
hard counter against it (well I did have one per-rest use of arcane dampener through an item but that was it). I grew annoyed and turned the difficulty down to story time where it still took forever, even with the use of buffs and debuffs (which I eventually ran out of). If I were to do this again (I likely won't ever) I wouldn't go in there unless I was at or near level 11.
I suppose I made that a bit harder for myself by not even going near a store except to buy camping supplies. I still don't regret not engaging with one of my least-favorite activities in a RPG. Anyway, that's proof right there that you don't "need" to vacuum up loot if you don't want to.
My opinion about PoE's quality remains unchanged. It just turns out that I was correct to avoid what I skipped the first time.