Only 10% of Scotland is arable land, most of the highlands and Islands is only fit for trees or moorland and rough grazing.
Subsidies accounted for 82 per cent of profit from farming, a figure which shows farming’s continued dependence on support payments.Livestock accounted for a third of output, with the beef sector, worth £715 million, the biggest earner.Barley 218 million milk 312million.

https://www.gov.scot/publications/total-income-farming-estimates-scotland-2016-18/pages/9/
If you make a cursory study of the relief, climate, soils and geology, it is obvious that a lot of the northern and western areas are very marginal for most kinds of agriculture.
Breaking up the huge Highland estates would simply replace an oligarchy making a fortune out of artificial desolation with thousands of smallholders living at subsistence level in the same desolation while it gets ever worse.
I would take issue with the artificial desolation. The highlands never has supported a dense population, especially when the clan system was destroyed during the Maunder minimum little ice age. Whether population densities increased during the medieval warming is unclear. Some argue the little ice age and concomitant famine did much to create the political union.