Many of these https://en.wikipedia.org/wiki/List_of_unicorn_startup_compan... could've been in theory done (to the point that there was no room for a multi-$b startup) by Google (Canva, Instacart, Telegram, Miro, Airtable), but weren't.

You wouldn't see them there. The vast majority of $100-500m ideas explored by Google are never actually turned into Beta products. They get killed during prototype testing and early alpha, because teams can get that far without meaningful VP sponsorship. But to get the investment required to scale from what a team can do with a UXer, a couple of volunteer SWEs, and a part-time PM ... you need exec support. When I was there, back in 2015-2016 we proposed several product concepts to Prabhakar that we'd already run detailed TAM analysis on, created business cases for, and tested in local markets. All of them estimated at $100-300m ARR. All of them rejected for being too small.

The plus side of allowing experimentation like this at Google, though, is that the work doesn't just go poof even after a rejection. From that core team of 5, two of them are now successful PMs, with one of them having "re-pitched" our concept of appointment booking to the Geo team as a feature addition for Google My Business. It was adopted, as was he, and that's how & why you can book appointments within Maps' business panes now. Another of them took one of our ideas into A120 and ended up mildly pivoting on the advice of the Travel VP. After some additional work, the project was adopted by Travel and is now why you get rich tour creation and destination exploration features inside of travel.google.com. A third member of our team - the UXer - maintained our team site with all the high-res mocks, business cases and pitch decks, and another one of those ideas was ultimate adopted as part of the Workspace team's investment in creating the "Gmail Hub" features that are why you have an expandable right pane with lots of app integration.

The point is not that my team was a bunch of anomalous superstars (we were not - just high achieving normal googlers), but that these kinds of things happen constantly within Google. For every idea you see on a Killed By Google list, there are probably 100 things that were killed as product concepts before release but ended up baked into one of the "15 products with >500m DAUs" Sundar referenced at I/O a couple weeks ago.