Having lived in a couple and now living in a multiple flat house built in the early 19th century I have a couple of thoughts.

Ceiling height. I am a large dude and with ceilings I can touch with my arm outstretched I constantly feel slightly claustrophobic (not in a pathological sense) like I'm in a cellar or something. I now have a ceiling that's going on 4 meters and the rooms feel so much bigger and brighter. I know it's harder to heat but I keep a cold flat anyway.

Size. Most of these flats are between 40 and 70 square meters. If you want something larger you're shit out of luck. The largest I've seen was like bordering 80 square meters. If you have more than two kids for example that might be a bit too small.

Noise insulation. You hear everything your neighbours do. I could follow TV programs without problems and the neighbours weren't exactly deaf. I've lived in blocks built in the 50s and late 80s, both modernised multiple times.

I am not a fan. There's middle ground. Multi family houses with two to three flats per story and and four to six stories are a nice compromise between space efficiency and comfort I believe.