I would think most size complaints would be about the thickness rather than the width of the phone. For me, and I accept this won't be for everyone, I'd be happy to have the phone much wider.
You're right that it probably does better suit quick tasks rather than longer use. For me I use my phone most whilst mobile so I only tend to really use the larger screen much when I'm at home. As a result I probably don't benefit from the larger screen as much as a lot of Fold users do. That's obviously no fault of the Fold and to be clear I'm not saying I don't love that big screen for when I can use it, just that I suspect I don't use it as much as most.