I think their uncanny valley metaphor is still apt in this situation though.
They’re trying to take design principles that are common among professionally designed webpages and apply them. They are, unfortunately, doing so quite poorly, and it is leading to a worse result.
Is it though? I’m not even a designer but I can see the color coordination isn’t ideal and a bit harsh. Sections are not delineated clearly. There’s isn’t a clear separation between heading and body in styling. These things are designer 101.
That's not really uncanny valley... so much as plainly amateur work.
I think its much more likely the greater volume of criticism is due to the fact that as OP gets closer to a known aesthetic, the precision of the criticisms can grow because it becomes more obvious what the goal is, and how its been missed.
Whereas a totally unstyled HTML page can't really be criticized usefully, because there is no real goal presented, and so nothing to really contrast against. At best you can say "fix everything".
Personally, when I open that site, I have no idea what it's about at all (yeah, it's something related to house-hunting). Only when I scroll down an entire screen-height, I get some high level explanation.
All the things you noted are there, but I don't think fixing them would solve anything.
They’re trying to take design principles that are common among professionally designed webpages and apply them. They are, unfortunately, doing so quite poorly, and it is leading to a worse result.
Edit: typo