Cigarettes, alcohol, crosswalks, cars, cows also have bad side effects, even on a “real” ecosystem, smoke, fire, deaths, pollution, etc…Saying the world will implode is hyperbole. The one thing cigarettes and sideloading have is that both ultimately are terrible choices for very different reasons. What they have in common is that second hand smoke has bad side-effects, while side-loading can have a bad side-effect on the ecosystem.
As you see we can play this game everywhere, it’s just about on which side you stand. In case of Apple it’s primary about securing their profits, nothing else. All the arguments against sideloading are pure exaggeration. Of course there will be a few collateral damages here and there, but forbidding all users to do what they want with their devices is the wrong approach. Just like forbidding crosswalks and cars because a few ones got hit by a car.