There's still plenty of EU pressure. This was a close enough thing that the EU spent months investigating it before making a decision.

That sends a pretty clear message to Apple "we're OK with what you're doing with messaging right now, but only just barely". If Apple does something the EU doesn't like, new legislation can be written.

There's also pressure in the USA and other countries where iMessage is far more widely used. The pressure hasn't gone anywhere yet, but it definitely could. The USA came down hard on Ma Bell when they dominated the phone industry. They're so dead most people have forgotten they existed. They were arguably the biggest company in the entire world at the time. Just like Apple is now.

Part of the order against Ma Bell was to order the company to stop selling phones. Imagine if the USA did that again, with Apple this time. I listened to an interview with an antitrust regulator in the USA yesterday (Decoder podcast)... he said they're short staffed and rely on punitive damages so harsh that other companies choose voluntary compliance, removing the need to actually regulate the whole industry (they don't have enough people to do that). Pretty scary stuff - the EU's approach is far gentler.