Numbers aside, SpaceX has a technological lead. They're not strangling competitors in a commodity business with monopoly practices. I wouldn't call ASMR or TSMC monopolies either, anyone can compete with them in theory. Standard oil, by contrast, would cut their competitors off from rail transit and selectively dump to drive them out of business.

The other reason they're not a monopoly is that they may do 90% of total launches, but most are for themselves to support starlink (another "nonopoly" with no competitors). They have 60% of the US government launch contracts, a small percentage of ESA when Ariane is flaky, amd of course 0% of China and Russia.