It’s not “luxury” if everyone’s enjoying it.
Correct.
In the case of China it's not enjoyed by everyone, though. A typical Chinese toilet is a huge hole in the ground with some kind of slabs of concrete over them, with a 15 cm wide slit between the slabs. You go stand on the two slabs and poop into the cavity underneath. There is typically a roof overneath. Homes often don't have anything on the floors. Just bare concrete.
The people living in opulence are not enjoying something everyone there has. They are enjoying something only the richest 0,5 % among their people has. China is a country where wealth is concentrated extremely strongly to the few.
Sure, if you ignore that the Maoist uprising against the landlords was the largest and most comprehensive proletarian revolution in history, and led to almost totally-equal redistribution of land among the peasantry.
That happened long before yesterday, though. If you look at decades such as 1970's or 1980's or even later, you'll notice that whatever Mao was striving for, got eventually all undone.