Despite the simple definitions, monopolies aren't about being forced to use their goods or services, or having no alternatives. It's about being unable to be threatened by competition. Basically lifting itself out of free market onto something where anything like illegal buyouts, market regulation etc can be simply paid off, fines and all.
The biggest myth of free market is that it self regulates. At this point even if you somehow got enough people to choose to not use Amazon or Disney it wouldn't make a difference. They could still operate at a 'loss' and get gains through massive amounts of wealth hoarding. (This isn't even harder for smaller titans. Tesla has only has one, ONE year where it earned a profit. Yet it continued to accrue wealth.)
And if someone somehow did make a rival product or service, they could use both legal and illegal hostile buyout techniques to gain it, because doing illegal business is just part of business since they aren't threatened by any normal fines.
It also makes places like Amazon and Disney ****ty places to work at because workers rights orgs can't get a leg in and it's easy for Amazon to just pay off safety violation fees.
The real problem here though, is that anti-trust laws havent been keeping up with complex digital markets, which involves all of the above corps. No significant law has been added in over 100 years. So despite the fact that there isn't a brick and mortar store in the world not effected by Amazon pricing, it's not looked at as a comparable market.