WeWork showed that individuals want and are willing to pay for communal office space and that small companies want and are willing to pay for "slices" of that space.
DoorDash (and the like) shows that people want and are willing to pay for more than just pizza and American-Chinese takeout and restaurants were willing to take a large percent cut for delivery-as-a-service.
Regus existed long before WeWork--as did many local spaces. I guess WeWork demonstrated that there was a market for "cooler" co-working spaces at scale.
As for DoorDash? People clearly want all sorts of rapid delivery and especially younger people who hate calling up a place really want to order through a consolidated web site. I'm not sure that's a revelation. The question is whether the economics broadly work out which is really not proven yet.
The value proposition that has changed with the delivery apps is that lots of restaurants can share the cost of a large pool of drivers with an app that can sufficiently allocate routes. This isn't a proposition that has actually been profitable yet, though, and really the only thing that makes this situation unique is that we are now in an unprecedented situation where indoor dining is recommended against and in some cases heavily restricted or banned entirely. Presumably when restaurants are free to operate traditionally again they might not find having such a low-margin delivery arm so great, and they will leave. Anecdotally, some restaurants did this in my area when lockdowns were eased up.
For example, there's probably a pretty robust market for a personal chef to come by your house and cook you a gourmet meal for $5. And private jets for the same price as commercial? Sign me up.