And yet, startups have been started as fully remote. Stack Overflow, Zapier, Seeq, just off the top of my head. And there are countless of successful open source projects as well.
Personally, while I agree that the bandwidth is higher locally, I don't agree you are prevented from expressing what you wish by communicating remotely; it just takes a bit longer, which is more than compensated by the time saved on other things.
I work at a fully remote startup, after working at a mostly remote startup before.
Having an easily accessibly video conference software, committing to getting employees good headsets, and enforcing videos on/1 person per screen makes collaboration very easy.
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The only thing that's missing is whiteboarding sessions (which seem to be more about fun than actual productivity). Instead, we typically ask a single engineer to write up a proposal doc then have everybody comment on that.
It requires a bit more lead time - write up, feedback, then finalization. However, the actual developer time is significantly less. One developer doing most of the work, with others chiming in periodically.
One day I hope everyone's equipped with a connected whiteboard (perhaps small enough to grab and take to the desk, but not tiny like a tablet) in their home office that works live in meetings.
But I'm not a huge fan of whiteboards in general. Of course one problem with offline whiteboards is that the information tends to get wiped away (unless someone's snapping and uploading photos), the other is that they tend to be messy and unsearchable and hard to edit & update afterwards.
IMO it's generally better to flesh out ideas in text. It's just that sometimes a figure or two, maybe a flow chart, would get the point across quicker. I haven't found software I like enough to consider it better than hand, but hand sucks too. I often brainstorm on paper, and run out of paper or end up having to squeeze stuff because I didn't start with things in the right place. A software solution would help.
I have to say, I've tried a digital whiteboard (Samsung Flip), and that thing was very cool. Wiping it (starting a new page) automatically saved the last into a history roll, and you could send them over email/network drive/etc. We made a draft design of a feature, then started a shared document from the uploaded picture made on the whiteboard. Worked quite well.
The main problem is the price, we can hardly afford one for each person, especially since it's not exactly something we use daily. Plus, even if we did, I'm not sure there's anyway to sync them in real-time.
Personally, while I agree that the bandwidth is higher locally, I don't agree you are prevented from expressing what you wish by communicating remotely; it just takes a bit longer, which is more than compensated by the time saved on other things.