Making such an argument is bound to look stupid when the premise is false to begin with. No amount of layers on top of this core is going to cover up how delusional Epic is.
Apple is monopolistic, of that there is no doubt.
The problem is that this case gives Apple more ground to behave how it already does.
Apple is no saint, but Epic is handing them legitimacy on a silver platter. No one company should have so much control over the usage of software over such a large portion of the population, and be allowed to enforce such strict rules that gauge money out of those forced to use their platform, and forces competition out of the race.
There's an issue with Apple, the government is already on the case of all big IT companies (there was a hearing at the beginning of the month). This case with Epic is just making things worse for consumers, because in the end it just means we pay more and more goes into Apple's pockets and, over the long run, we have less options due to less competition.
My problem with this is that there's literally not a single person that's "forced to use their platform". Even if you "had" to have a phone there are other options than getting an Apple one.
Plus I know you're talking about the US government and I don't know how it is over there, but as a Brit I know the UK government wouldn't have a leg to stand on if they were to criticise Apple for this since they're much worse when it comes to monopolies (TVs), have no competition unlike Apple, and will send you to jail if you don't pay them while Apple won't/can't do anything if you don't pay them.
I don't really see how this Apple winning would make things worse for consumers though. It would just maintain the status quo, no? Apple would still get their 30% cut, just like they always have. The competition would be pretty much unaffected either way too, so why would things be worse?