Let me try to help. What some people want is what they see as the superior phone: iPhone... with more options for sourcing software to enjoy on that phone. They don't want the inferior phone enough to then get a greater freedom of sourcing software. Like just about anything we buy, consumers want the best of both.
All of us already have the desired app freedom of source choice on our Macs. iPhone buyers would like access to iPhone apps just like we Mac owners can access Mac Apps.
There is an Apple Mac App Store too. But we don't have to source all Mac apps from only that one store. I have a number of Mac apps I've picked up via those 10 apps for $5 bundles. When do you see that sort of bargain in the iOS App Store? I often go straight to the developer's website to buy an app for my Macs... so they make as much money as they can make for their creations. I can do that- if I choose- OR I can buy the same app from the Mac App Store so Apple can take the first bite of revenue from that purchase, even before the app creators.
Competition is not purely A vs. B. There can be competition or even up to monopolistic practices within just B. Customer interests- whether via policy or just customer wants- tend to near universally want freedom to get what they want for least possible cost. We tend to do that in nearly all purchases. We want an ability to shop around to find what we want for the lowest price. How do we shop around for iOS apps? We can't. There's just a single iOS store... unless we live in the EU.
When a company gets a lock on any market (not limited to just software apps), that company can set nearly any price for that market... as well as restrictive policy for buyers within that market.
Change the name involved to anyone else. How about Shell Gasoline? Would we like the only source of Gas in our country to be from one company? Would we want only one source of grocery in our country? When we change the name, our consumer mind will wake up and recognize the undesirability of no competition.
But, but, but, there's android in this situation. Yes, but when one buys an iPhone, they are then locked into a single Company Store model almost everywhere except the EU. And to then use that iPhone with any software, they have one single choice of where they can get those apps.
Perhaps consider it another way: effective immediately, the only place you can get Mac apps is the Apple Mac App Store. No more bundle deals. No more buying from developers. You can only buy from Apple. If an app you like is not in the Apple Store, you can no longer get that app. Do we welcome that wholeheartedly after enjoying the freedom to get apps from many sources with much competition for all the years Mac have existed?
If that's too close to (Brand favorite) home: effective immediately, you can only get cell service from AT&T. No other source of cell service may be used with your iPhone. Pay up for whatever AT&T demands with this lock on that market because it is your only choice. No shopping around for better deals. If AT&T now dominating this market no longer wants to give away a phone on contract, pay up for phone and then pay whatever they want for service. Don't like AT&T total lock on the cellular market? Throw away your iPhone and buy Android. "But I don't want Android!" Tough luck. If you want iPhone, give AT&T whatever they want for service. You have no choices.
If any of that gives you pause, we shouldn't be so quick to defend preventing that kind of consumer flexibility for software apps for a different kind of Apple computer than our Macs. Our brand bias/Apple love/"Apple is my God" positions cloud how we see the issue. Step back from that- mentally change the "Who?" and see if we would argue for the same way FOR maybe Samsung, Microsoft, Google, Spotify, Netflix, etc with the same zeal & passion. If not, it shouldn't be different just because our favorite company is the name involved.
I hope that helps.