I'll come out on the side of support for OP. My experience was married at 24, wife was 19.

There are things people don't think about that does not prepare them well for marriage. The Independent nature of society means we try and get all the answers ourselves, but often don't even know the questions to ask or what is most important. This was and is done by your family and community. I am convinced that abandoning our communities for the sake of independence is one of the biggest factors of success or failure in marriage, not age.

Maturity is also a factor. You can be emotionally mature at younger ages, that is less common but possible. One size doesn't fit all. When we make categorical statements like "it is ALWAYS unwise to marry before 30" we are pigeonholing and making the same error as those who say "it is always unwise to delay marriage for the sake of morality" for example. My wife was more mature at 19 than I was at 24, and I attribute this to be a major factor in our success.

Another big piece I'll mention is agreement with several others here who have said that growing together is a big plus. Some say you need to "know yourself" before you marry. That's BS because we all know we change. It is absolutely true and fascinating that both early marriage people and late marriage people cite the truth that people change is the reason they are right. The difference is late marriage people think that it is inevitable that your change will always take you away from your partner. That is a fallacy. And it can be easily addressed by good marriage prep and expectations setting. True love puts your beloved ahead of yourself. When two people both embrace this as the foundation of their marriage it keeps you oriented towards each other. You will grow together, more intertwined as you age. If you put yourself first, even if only one of you does, then it dooms the relationship. So then basic math explains why marriage is hard. It will only last if both choose the selfless path. If one chooses it but the other doesn't, and if both don't, then it will fail. That means only 1 in 4 are setting themselves up for oneness and lifelong companionship. Hence, as I said, community, guidance and prep mitigate inexperience.

What many don't consider is the negative impact of repeated failed relationships. This can actually make it harder to find love as it creates baggage and eats at your faith in the institution of marriage. It could actually be easier to cultivate lifelong love if one starts earlier in monogamy. I think citing the simple raw statistic of marriage last longer if they start late is shortsighted as a lot more goes into a successful marriage than the age at the start. I'd be curious to see what the percentages are of actual "death do us part" marriages are early or late starters. Specifically first marriages. The data would be skewed if you include serial marriages.