You're correct, but in this case it's clear Microsoft doesn't have a monopoly on spreadsheets. They just make the best software. They aren't bashing vendors over the head with Excel, etc. IMO the case for Apple or Microsoft being monopolistic is pretty weak compared to Google, Facebook and perhaps Amazon. Apple has a problem because it's such a walled garden. Microsoft generally doesn't have any of the problems the FAANG (sans Netflix) companies have.
This, currently on the front page...sure doesn't sound like Excel is a monopoly https://foundationinc.co/lab/the-saas-opportunity-of-unbundl...