To unpack “Ricardo's labor theory of value might better be described as a labor theory of cost or a labor theory of constraint”:

Neoclassical economics is trying to answer "how much value exists?" in order to recommend policies that produce more of it, and uses willingness-to-pay as the measure. This gives you consumer surplus, GDP, welfare theorems, all attempts to quantify the total good being produced. Under this framework, more transactions means more measured value, because each transaction reveals that both parties preferred the trade to the alternative.

Ricardo isn't trying to measure how much good is being created. He's trying to explain why things cost what they cost. The answer is the labor required to produce them, which is the binding constraint on supply. A thing is expensive because it's hard to get, and "hard to get" cashes out as the human effort needed to produce it (or, for something like land or a mineral deposit, the effort needed to obtain the next best alternative to it).

Ricardo's framework doesn't have a concept of aggregate value being maximized. It has constraints and prices. You can ask "did this get cheaper or more expensive to produce?" but not "did total welfare go up?" This means it can't generate the neoclassical blind spot where forcing more market participation registers as creating more value; there's no "total value" variable to be inflated by counting transactions.