If e2ee became common, Google would offer a way to upload your private key or generate it for you (like proton mail does, IIRC), so you can conveniently read your mail in the web client, undermining the whole idea behind e2ee.
Does it undermine the whole idea? You can just assume that everyone with a @gmail account may be compromised (just like people with work email don't really own their mailbox), and keep your secure communication with the others.
I mean yeah, the point the article is making would be true non the less, so e2ee is not the answer to the problem.