In Europe we have plenty of old buildings. The good ones (i.e. made by very wealthy people) tend to be decent, with a skew towards huge living rooms but tiny rooms. The cheaper ones are a mess to mantain: cold in winter, hot in summer, expensive to renovate (it could be more expensive to renovate than to build a new one), bad to no isolation, in my region terribly humid, usually too dark with minuscule windows for modern standards.
With roman buildings that last 2000 thousand years we are looking at survivor bias. Near me there are some roman ruins from a (cheap and small) public bath that are barely distiguishable from a pile of bricks. The are some nearby pre-roman ruins in better shape.
>cold in winter >in my region terribly humid
You need to actually reduce draft a bit (often old houses like mine tend to accumulate flaws that the elderly living there before didn't fix anymore.) and use a heating sources that matches.
Having a fireplace is fine. It could overheat the house whilst also keeping air dryer and it's essentially renewable (compared to the alternatives and houses made of more plastic insulation than anything else) if you don't mind air quality dip in winter.
That said i can see how that's no longer an option in places that have drastically increased their population
Fireplace is extremely inefficient, and really bad for both your (exhaust fumes get into the room anyway), and your neighbors (the smoke doesn't just dissappear) health, though.
I love the heat and smell of a good fire as much as the next guy, I'm just not sure it's worth the risk of cancer and respiratory diseases.
If efficiency is important, like if you are using wood for primary heat, you should at a minimum be using a sealed box stove which should be pretty efficient and have little to no smoke escaping.
Alternatly you could just use an outdoor stove that merely heat exchanges to the inside.