I don't have the experience of living in US-style McMansion, but I think I would loath to do all the necessary cleaning, repairs, mowing the lawn, etc. I really don't want to spend most of my weekends doing that.

I said that at my last place. It was a pain to clean and I wasn't getting any benefit out of the space (admittedly that might have been different had it not been lockdown and I'd been able to invite friends around).

Well first of all, it's not "I wish I had less space" but rather "I wish I had the goods and experiences I had to forego in order to obtain and hold onto this extra space".

But anyways you're missing the point. For instance my house had a 'dining room' when I bought it, but I made it into something that I use every day (music studio/band practice room).

The conventional part of me would have just kept it a dining room, and used it maybe once or twice.

Ok, I indeed misunderstood your point then, because I did the same to dining room, lol.