AFAIK this is just Apple-approved apps, just through another app and servers. How does this change anything ? Apple still has full control over what apps users can install. There is no side-loading. They still need to approve every app on third party platforms. Or has Apple actually decided to remove app signing? They sure didn't when they announced this change.
So yes, what they did changes anything, and it's just a smack in the EU face while keeping the status-quo. If they wouldn't maliciously comply and do some weird acrobatics we'd have a fdroid-like stores running right now and options to enable side-loading and some kind of scanning feature like google play protect (which on the other hand, likes to turns itself on).
For the user this is really simple: you're a typical consumer who wants to use appstore and stick to apple-approved software just to be "safe" - that's the default for you. You are poweruser who wants to expand the software library on the device - tap the setting, read the warning, read it again and install whatever you like
Anyway, it seems that the EC has received feedback from devs regarding what apple presented: https://www.macrumors.com/2024/03/20/eu-antitrust-chief-warn... so things may change in the future.