It's true there are risks. But the argument for capital's income based on risk begs the question.
Let's suppose all the means of production were owned in common by the community and the community makes decisions about allocation of resources to production, including our own labor and other inputs.
Even if people now make predictions about what they will want..and this is better info than the capitalist "market researchers" have...things can change for a variety of reasons. People might come to no longer what this product as much but the resources could have been used to make something much more in demand.
But in this case it is the community that assumes the losses.
So, we can agree with the principle that whoever owns the means of production will shoulder both the gains and the losses, and hence the risks.
But why should it be a minority of capitalists have this power? The argument for capitalist income based on risk thus begs the question because they are already assuming it is legitimate for the capitalists to monopolize the means of production and hence gains and losses from that fact.
The "risk" argument is entirely circular.
The emancipation of the working class must be the work of the workers themselves.