I do find it interesting that your social circle is willing to bet their entire net worth on a risky startup where the reward is a salary cut in the worker cooperative + some savings account level interest. The "funding" bit is the key. You waived over it with crowdfunding, but now it's like buying lottery tickets with low payout. Pay $20 for a 20% chance at $40 in 10 years! You'll make the world a better place!
Really what the parent is proposing is something like -
Here is a savings account. You can throw chunks of money in it at startups that have a high chance of failing. But if they succeed you'll only earn bank level interest since it's not capital investment. So you have a small chance at earning bank level interest.
Where is the incentive?
It's not "could", it's will. With 100% certainty. The only question is how many and hard they will be to control. We know this because it has happened before.
I know any number of people who would eagerly start a high risk innovation play as a worker cooperative, because the money reward isn't what they care about. They care about making change in society or seeing a technical advancement become wide spread.
For most of them, they just need the chance - a floor under their feet so they can't fall too far if they fail and enough funding to get going. And, given how much crowdfunding has succeeded in todays world of concentrated wealth - I believe crowdfunding could provide that in this system where wealth is much, much more distributed.
The other piece of if is, with worker cooperatives every single employee of the company is fully bought into that innovation play. And stands to see the rewards created by it. Not just the investors and company founders. If anything, it increases the effectiveness of these companies, because everyone involved in them is incentivized to give it their all. Everyone involved stands to see the rewards of success.