Worrying about browser engines was always misguided. Letting 5 people use Gecko will be fantastic until Gecko is so irrelevant that even those people give up.
Vendors like Microsoft having a large userbase attracted to good, reliable software to counter another browser’s overt influence was always the solution. It’s all about users.
25 million people on Firefox is not enough. Neither is 5,000 that switch their rendering engine in iOS. Firefox needs users for relevancy, not its own engine.
To be clear, I’m not outraged by this EU edict. I’m saying it’s irrelevant and misguided as most regulations are.