Anytime someone starts talking about lowering the age of consent, no matter how outwardly fair or reasonable their opinions seem, it's always for nefarious reasons. If they say they just want to marry 16-year-olds, they're lying, it's not the end goal it's a goalpost they'll move the instant they achieve it.

There is an argument to be made that winning the war on teenage pregnancy (in tandem to extending adolescence well into our 20s) led in part to our current population collapse, but it's one I won't even touch since everyone who does always does it because they secretly want to fuck 12-year-olds.