Yeah, I also question the distinction between a 17 year old marrying a 50 year old and an 18 year old marrying a 50 year old. Does your judgement suddenly magically get better after you turn 18?
What I see is that we shelter kids from reality because they're just kids, then these kids grow up to be irresponsible adults, then in turn we create more rules about sheltering "young adults" from consequences. It's a feedback loop.
The thing you should be feeling now after reading that is shame.
Adulthood used to begin at 13 or so across the world. That didn't mean a 13 year old was going to run the tribe or anything, but then, a junior developer doesn't run the software company either at 25. But adulthood meant having responsibilities, obligations, and being expected to make your own decision. Our school system is designed very specifically to prevent this from happening.
Given that, it does sort of make sense that IF you're being subjected to that sort of psychological abuse, perhaps we can't expect you to be able to make responsible decisions. Those who can generally are the exception, not the rule.
Perhaps rather than drawing all these lines though, we should be seriously considering getting rid of a school system that was modeled off of the Prussian model, which the Nazis were known to enforce, and which is still the ONLY option even in modern day Germany, regardless of how much the parents want to or are capable of home schooling children.