Yes, the entire part of town that they built and maintain. And if you don't like it, there is a whole "open" other part of town where you have a bunch of really great options.
It's like moving into a neighborhood with a HOA and then getting upset you can't paint your house purple. Do I think it's ridiculous an HOA says you can't paint your house whatever color you want? Absolutely. But you knew that you couldn't when you bought the house!
Do I think it's ridiculous Apple is kicking and screaming about this? Yes. Do I wish they'd allow side loading? Personally, for me yes - but I think it's going to lead to more issues with normal users than people who want it realize. Do I think the EU should be able to force them to? Absolutely not. Do I think that my (or Apple's) opinion matters here? No - the EU is going to do what the EU is going to do.
I think the point is that mobile platforms are now where a huge amount of computing use and commerce now occur.
Apple makes a compelling consumer product which people love.
Most people have no idea - nor do they care - about the business terms that Apple dictates in the App Store.
Ie so they are not going to change devices (unless Apple stops making good iPhones, or something better comes along).
So what the EU is doing is making mobile platforms open so that they are regulated and competition is allowed across mobile platforms in their jurisdiction.
Competition is good right?
Apple is doing the classic thing that antitrust regulation is there to prevent.
Where first movers make a land grab, then get huge rewards from this in the early and middle years of a technology revolution (which no one tends to begrudge, regulation wise).
Where things are frowned upon, are companies that then milk the benefits of that land grab, without doing too much work for huge profits. And this is exactly what Apple is doing with the App Store.
You could make the argument that it’s the USA who is failing to properly regulate their mobile platforms so don’t be too harsh on the EU.