Well, you are saying that everything can be done by coding, I don't doubt that, I doubt how good that coding is. How well apps are reviewed before going on sell.
I doubt the new-store boss would cancel old incompatible apps, turning down the number of apps available in a market where that number would be crucial.
But then again, the development tools would have a higher cost, the consumer could have all those negative impacts we were listing. What for? To give Epic and other big companies a higher margin?
Can you list positive impacts to the end user other than saying "competition among different markets is good", what is this "good", in this case.
We won't get lower price, cause if the developer know we can pay 10$ for 10 gems, we'll pay 10$, we won't pay 7$ just because the money wouldn't go to Apple, because they planned to introduce charting adverts.
Sure thing, just build a general AppStore and a Store API, this does not even have to be made by Apple.
There are also uncountable macOS update mechanisms as prof of concept(e.g brew cast, MacUpdate), which could easily be adapted to work on iOS wrapped with a shiny UI and a decent working TopChart. We had TopChart Apps already before they anti-competitively got kicked out by Apple, and that just to prioritze their Store charts and sell ads there.
And there are also prof of concepts for alternative iOS AppStores, e.g. for jailbroken iDevices which works flawlessly, also that other one which runs trapped and limited by Apple over Testflight(iirc. called AltStore).
Personally, I also see no benefit of a AppStore compared to an App which comes with its own Update System or e.g. with something like the Sparkle Framework. There are uncountable ways to create something like that in a comfortable nice way. The benefit would be even to be able to run older Versions of an App, or e.g. to rollback because of a bug, whatever.
Anyway, I think I don't need to post a list with positive impact of market competitions, just look around you.
The whole world just came that far, because of market competitions.
But yes, an alternative AppStore won't stop filthy scumbag developers from exploiting customers, e.g. as Apple is doing with their monopoly in a much worse way. Getting all pre-crewed is not the right way, we need to be able to choose what's best for us.