Consumers are not the consideration. You as a user of Meta's software have no expectation to do something outside of Meta's ecosystem. That isn't an anti-trust issue. You may not like it, but literally EVERYTHING YOU DO is somehow decided or defined for your in the way software is written.
"Competition" would be giving users the ability to choose which AI suite they want to use.
Users have this. Meta can't block Apple from being used (and doing so would be an antitrust violation). Fire up an Apple app, write what you want and copy / paste it. Or better still stop using Meta's products if you don't like how they work. Not integrating Apple Intelligence in another AI product isn't the lack of competition, it is rather something called "absolutely obvious common sense" from a business and a consumer expectation point of view.
What I do wish however is for an option to turn all this shit off. I don't need a dedicated button to speak to Meta AI in WhatsApp, nor do I need Apple Intelligence to write my messages for me.