One thing that is worth pointing out is that there are some realism considerations that should be kept in mind for door heights. In general, most medieval houses that were not particularly wealthy had to be very sparing with openings in their houses, whether for windows or doors.
- Large doors required more heating in the home because the opening created draft and allowed more cold air to enter. Remember that houses were not insulated, and every little thing that adds more cold air will require more time and resources to mitigate.
- Larger doors generally require more advanced carpentry to accommodate the heavier solid wood (think of the hinges, joints, studding etc that need to be made to support this).
- Structurally, the larger an opening in a house is the more careful your weight distribution and bracing needs to be to prevent having an unstable house. For this reason most medieval houses avoided large openings to ensure a more secure and solid structure.
- The resources needed for a larger door (when I say large, I mean over 2 meters or 2 - 2.25 blocks) is generally just going to be a lot more expensive and it should be taken into account if a certain house has the means, or desire, to attain that for very little benefit.
Crouching through doorways seems a bit of a non-issue in my honest opinion, considering that also happened IRL as well. Rather than facing the above-mentioned issues, a house owner would much rather have simply crouched under the door lintel to get in and out. This is effectively (and actually rather fortunately) represented in Minecraft by shifting, so the immersion you experience is actually accurate to how it should be.
Now, for a place like Minas Tirith where the average Numenorean (and correct me if I’m wrong here) is 6’4" tall, maybe sub-2 block entrances are not needed, or desired due to the urban resources at their disposal and opportunity for more advanced and refined masonry. That being said I will not opt out, even in MT of all places, of using smaller doors considering the benefits and applicability is just overwhelming. Definitely not everywhere as can be obviously observed, but in some poorer places they absolutely make sense.
In Bree-land, based on the realism that is desired (as all projects are), I think it’s only fair that sub-2 block entrances in some areas are present (even though if we’re honest it would actually be practically every door, but I realize some concessions need to be made). There are of course some lore considerations with older Arnorian buildings having more affluent masonry, but unless a building has been standing (WRT its arches and openings) since those times, which I find difficult to believe because buildings change incredibly much over time, there is no reason to have anything like we have in MT - size-wise.