I don't know enough about Hey to judge that, but to me comparing Notion to Google Docs is like comparing Slack to Gmail. I mean sure, both Slack and Gmail are communication tools, but they solve for different use cases so they're not really interchangeable. I can imagine that if your use cases are all things that Slack is better at you might think "Wow, Gmail is so outdated and horrible why isn't it like Slack?" But personally I like having both because I have use cases that email is better for and I'm skeptical that one generalist tool that tried to be useful for all use cases would be particularly good for any of them.
Getting back to Notion and Google Docs, I'd rather use Notion for internal documentation and I'd really, really rather use Google Docs for redlining contracts, which is most often what I'm doing when I'm dealing with .doc/.docx files. In Microsoft's suite I think Notion is an alternative to OneNote, not to Word. So I would agree with the author if the implication was that Google should have a Notion-like tool in addition to Google Docs, but suggesting that Google Docs is bad because it's not Notion-like doesn't make any more sense to me than saying that Gmail is bad because it's not Slack.