It literally is "everyone must immediately not implement anything that cuts into Apple's bottom line"

Apple has veto power over what becomes web standards now. If they didn't abuse that power, and also forbid other browser engines on iOS, then there wouldn't be a problem. They abuse their power in a way that hurts everyone but Apple, and the DOJ took notice.

You say Firefox doesn't implement the same APIs that Apple won't as proof of something, but Opera and other browsers do implement those APIs, so that really cancells out whatever argument you thought you had.

Back in the day, Microsoft invented XMLHTTPRequest, and if Apple had veto power over web standards back then, the web might still be "Web 1.0", hypothetically speaking.

But now Apple can block progress in web browsers now, and the DOJ will likely prove that they are abusing their position to the detriment of everyone that uses a web browser, so Apple can make a few more dollars from their app store.

It should not be so difficult for anyone to understand.