Right. But you already admitted that going to another store was mostly due to the app either not being available on the Play Store or that the Play Store version didn't work as well (like with your DJI drone). You weren't going to other stores to get bargain prices relative to the Play Store.
Like I said, the EU isn't doing this because going to another store "works fine". They have always claimed it's a competitive issue. Also like I said, the EU has never provided any real world studies comparing pricing between the various "open" (Windows, Android, macOS) and "closed" (iOS, iPadOS, Xbox, Playstation, Switch) systems. IMO, they intentionally avoided doing that because they knew it wouldn't support any of their claims per consumers.
If you have a monopoly, it will behave in a monopolistic manner. If you have competition, there will be competition based on price, quality, or maybe something else, such as user experience. Monopoly is the least favoured market arrangement, unless it's a natural monopoly (economies of scale dictate that it needs to be a single supplier), as it leads to sub-optimal outcomes for the consumer, and excess profits for the monopolist.
This is first year classical microeconomics.
Within the market for iOS apps, Apple has a monopoly on the distribution of those apps.
Looking at it from the perspective of app developers, Apple is a gatekeeper and can prevent other app producers from even competing at all. At its heart, that is an anti-competitive market structure.
Every developed country has a Competition Authority or Mergers and Acquisitions Body or similar to promote competition and competitive markets, because monopoly is quite rightly regarded as a market failure, leading to higher prices and/or worse service. This is no different.
In the long run, this might help Apple - it's no longer under pressure to host all apps as it's no longer the only show in town. It can get very stringent on it's standards for apps, ensure only good quality apps make the App Store and say "Well if you want rubbish, go over there to that store..."