Dense means a strained infrastructure, congestion of daily life, and -not the least- makes it neigh impossible for average Joe to own some real estate. The last point is a severe factor for gentrification IMO.

Now the countryside on the other hand is, at least here, partially empty. Population shrinks and villages collapse. The elderly live in deserted ghost towns. Existing infrastructure cannot maintained. This is not wild nature out there but rather a dystopia.

You are confusing correlation for causation. Dense doesn't mean average Joe can't own real estate; it's just that both density and high prices are both effected by a common factor (high demand). But you plan for both density and affordability.