There isn’t enough time between labor being performed and it being paid for inflation to have much effect. Long term capital investments have plenty of time for inflation to pile up and distort the naive calculation of “gain”.
For practical reasons the state does not demand the tax until the accumulated gains have been realized by selling the asset. This makes sense for illiquid assets like stock in your private startup, but I don't think it should change the calculation of when the tax was incurred and how much. For liquid assets like shares in public companies, I think it would actually be perfectly reasonable to demand the tax on unrealized gains.