To collaborate with someone else, you need to be in the same silo.
The difficulty of finding a silo everyone you want to collaborate with is already in scales with the square of number of participants (n).
And then having the relevant data/context in the silo per person scales with the square of the number of participants, too.
n2n2 = n4
This is a massive headwind.
Even if there were a piece of software that did precisely what would be most useful for that use case, you'd have to overcome a hurricane force coordination headwind for it to be viable.
Everyone just uses the lowest common denominator: WhatsApp and Google Docs.
You might erroneously conclude that no one wants this… but it's more that it's not possible, so no one even thinks to dream that it might be possible.
So the bespoke collaboration software is possible to exist, but not viable.
So no one bothered creating it in the first place.
Now, LLMs can create custom software on demand… but they can't solve this coordination problem.
An app would have to be better by 1000x than WhatsApp to be viable to coordinate with in today's physics.