Right, but that doesn't change the return. It would only change the amount of money being invested in VC or IPOs versus bonds. And the total money chasing stocks isn't evenly distributed amongst stocks, so less money in the stock market doesn't necessarily mean a lower valuation for a particular company (such as the big winner in a VC portfolio).
The risk free return is an opportunity cost. If I invest $10 and get back $11, the net is $1 regardless of whether bonds yielded 0% or 100%.
And that cost is taken into account when people value the merits of a particular investment/company.
If bonds yield 100% p/a then an investment with even a decent potential payout in 10 years time will be seen as worthless.
But one that is likely to pay out a dividend tomorrow may not be.
That’s the whole premise behind discounted cashflow analysis: mechanistically taking into account the opportunity cost of the risk-free interest rate to derive a valuation.
The risk free return is an opportunity cost. If I invest $10 and get back $11, the net is $1 regardless of whether bonds yielded 0% or 100%.