Earlier quoted context omitted.
Tuta, Fastmail, and Posteo are all much better alternatives to Gmail in terms of privacy. My comment, as per subject, is about Gmail.
His point was just that many business users can only purchase Google’s solution or Microsoft’s solution, because they’re the only services that will offer interoperability with many other security and compliance services and advanced functionality like SSO, third party email scanning, compliance journaling etc. The email market is essentially a duopoly as soon as you need any functionality beyond basic email.
No, you don't need either of these companies if you need a corporate stack for communication and collaboration. And anyone who believes Microsoft or Google is doing anything out of the ordinary to protect their users or data is out of the loop.