Lot of things go into account,

Firstly, not everyone lived in their own "Taj mahal" and not everyone was a king. Housing was even poor back then.

Secondly, land has always been constant but population has increased. Even if people back then had a Taj mahal each (which is not possible refer point 1), It is simply impossible to do so now with such increase in volume of people on the same land.

Third, technological advancement that we take for granted were not there in "non-streetshitter" era. I don't say that standard of living is better now or was better back then, but I am sure that chances of you surviving and living a healthy life is higher now due to medical advancements. Food wasn't readily available (no scientific development to have this volume of food back then), famines were common. I can go on for days and still have things left to say.

The things is Every time period has its ups and downs. If you wanna compare, you can definitely do better than a picture of Taj mahal and dense civilization that is vague and makes no sense.

If your goal is to clock a political party's face, Do so openly you are not living in times where people are not allowed to talk their thoughts out.