Isn't this a circular argument? The question was what "useful" things do these crypto solutions/companies provide, and your example is a product which allows regulated entities to invest in crypto.

"Why is X valuable? Because X allows you to invest in... X."

Also, in this specific example (Arc), is the solution even considered DeFi? There's a centralized list of whitelister entities and you can only participate if you're a customer of these entities. So they're like banks.