Chrome, on the other hand, is worth worrying about. Unlike the other technologies you mention, it's a consumer application that legitimately lets Google apply Microsoft-style embrace-and-extend tactics, monopolizing the web and steering it in a direction that benefits Google more than anything (e.g. ads and tracking).
Kubernetes may have come out of Google, but it isn't even in their control anymore. If anything, Kubernetes is a strategic play to democratize cloud orchestration, undermining competitors such as AWS.
"Releasing these things don't give them control over anything that negatively impacts users" and "undermining competitors such as AWS" contradict with each other if you believe competition is good for users. The decision to release something as open source doesn't happen in a vacuum. Open source doesn't automatically make corporate activity morally good or neutral.
Specifically in the case of gRPC-Web, even though "it's open source", does every gRPC service exposed on the web provide a .proto file for you to build your own client? If not, that's a big step down in terms of power given to end-users compared to REST.
To your point about .proto files for public endpoints: does every JSON HTTP endpoint exposed to the web provide documentation for you to build your own client? (of course not)
Re: public endpoints. Say you're poking around a public web service, and it doesn't provide an API. Maybe you're writing a browser extension. Would you rather reverse engineer a JSON HTTP API with no documentation, or a gRPC-Web API with no .proto file?
You’re welcome.
If Google is effectively a monopoly, does it matter if you could theoretically replace all of its offerings? Think about other monopolies in history, I'm sure they had "replacements" too.
As for the Chrome login thing, being logged in on Chrome does not in any way shape or form alter the way in which Chrome interacts with non-Google sites or services. So I don't see how it is an example of how Google exercises control over the web. Certainly not in a world where I need only drag Chrome into the trash can to switch browsers (and, indeed, on a computer where Apple constantly exhorts me, in a way I cannot disable, to switch to Safari instead).