Ricardian thought in progress

In Ricardo's basic model there are diminishing rather than linear returns.  Surplus accrues to the fixed factor, which is land.  Labor earns some version of subsistence and the going rate of profit is piled on top of that.  The productive difference between a piece of land, and the least valuable piece of land, accrues to each specific landlord as rent.

What if ideas rather than land are the fixed factor?  Wages and profits stagnate.  Some "idea landlords" receive enormous pecuniary returns, while others do not.  The rate of invention is slowing down and indeed "patents per researcher" has been falling for a long time.

Which features of our evolving income distribution does that scenario not fit?

Addendum: Arnold Kling comments.