But basically nothing of that is something capitalists personally do.
Logistics ? Drivers, warehouse-managers etc.
Demand ? Market research and Marketing
Development of new products? R&D
It is all people working for wages, aka workers. Doesn't matter that some are white collar.
The only thing a capitalist actually provides is capital. And there is no reason why that contribution is the only one worthy of the profit.
First, all of those are things capitalists do. Including labor. A capitalist is one who owns significant resources and uses them towards the end of profit, that designation does not preclude also doing any of the work. Of course you can have useless ownership, but you can also have terrible employees, so it seems unfair to focus on just one. But for the sake of this argument, we have to first decide that we are talking specifically about someone who only provides capital and is otherwise useless, which we can do, because that's not the real issue with your argument here, that's just me being picky.
The real issue of your argument is a matter of definitions. You say that capital contribution isn't the only one worthy of profit. What you should be saying is that other contributions are worthy of compensation, and they are, and they are compensated. And the profit by definition is what is left over after all costs are paid, including the compensation of workers. Imagine I own a company with 9 workers and myself, and at the end of the day we profit $10. As owner, that money is mine. Maybe I decide to share that profit equally, and give everyone a $1 bonus, and then everyone has gotten an equal portion of the $10. Did they get profit from that? No, they got more compensation, my payroll went up $9, and the profit reduced to $1. Abstractly, I can spread out the wealth and share with my employees, but definitionally, they will never have the profits, because giving it to them means it's no longer profit.
Unless you, like Seanchaidh, want to take the position that providing capital is not worthy of any compensation at all, you have to look at each case independently to determine whether the workers are fairly compensated and whether ownership is fairly compensated. That there is profit does not indicate that. it only indicates that ownership was compensated at all. And conversely, in many cases there isn't any profit and the revenue still isn't fairly allocated. You can't just say "well, there was profit, someone was exploited" unless you want to take the strict position that the decision to deploy one's wealth towards a certain enterprise is the singular action that nobody should ever be rewarded for.