I have wondered much the same. Wiki gives a population of about 5 million, or 200 per square Km, England having about 395 per square Km. So less crowded than England, but still twice as full as France at 97.

I watched the series with interest, having enjoyed the books very much and wanting to see if my mental pictures were anything like correct. They weren't.

The characters are somewhat different from my imagination, and there have been the usual adjustments in plot to accommodate the different format, but a far better adaptation than many such.

For me the biggest revelation has been just how barren much of the island seems. The dry stone walls and the farmsteads seem very much like the Yorkshire dales, but with blistering sun as 'normal weather' to replace torrential rain. The towns, urban views, and buildings are like nowhere I know. I am seldom tempted by hot places, but I reckon a winter visit could appeal.