I think you're being unreasonable. Also, not very mature. If you say you are capable - why can't you decide who to have relationship with? If you've made a mistake you accept it and move on.
Why are adult's choices the responsibility of their parents?
Are today's young people being brought up to overly rely on parents being there to hold their hands?
At 19 I had just acquired a mortgage with my then boyfriend. We married six months later when I was 20. I've been married 34 years. Not saying it's been a bed of roses but we're very happy with ourselves/our families. Our children are very happy to share their families with us (corona permitting) we have close relationships with all of our children and our in-laws and wider families. (Not saying everyone is 'perfect' but we all get along and treat everyone with respect.)
Nineteen year old's are entitled to make life decisions.
Everyone learns from their own mistakes. People generally don't learn from other people's hindsight.
Both of our daughters met their partners when they were 20.
Both of my daughters have partners who are 13 years older. They both own their own homes. We have four grandchildren.
Their partners are loving and supportive (great personalities) and their partners' families are lovely. There is nothing controlling or perverted about either of them. Neither of their partners have have children from previous relationships.
There's nothing wrong with making these sort of decisions at a younger age.
Lots of people on here regard women in their twenties as 'young mothers' in a derogative way because the current trend is to have babies at a later age. I had the term elderly primigravida on my maternity notes as I had my first baby at 25. My own mother had children at 33 and 35 yrs so it's not new. I am so happy to have had my children ten years younger than my own mother because I can do lots more practical things to help my children/grandchildren. My parents were 60 when I had children and both in ill-health but I was a SAHM whilst my children were older - my daughters' salaries are needed for them to live comfortably.
Both my daughters commented on being made to feel bad because most mothers to be at their appointments/in their experience were older and in cliques which excluded younger mothers.
Why are couples who have had families earlier looked down upon? I'm so happy that my daughters started families in their twenties - it was right for them. They can now continue to advance their careers. I wouldn't have dreamt of saying 'your partners are far too old' or 'you're having children far too young and ruining your lives'. I respect any decision they make. (Although I have not agreed with some choices - I have stood back and let things go.)
Why should parents be made to feel guilty for not intervening in the decisions that another adult makes?
We offer advice and help (I've looked after my grandchildren when their mums return to work) when asked but wouldn't dream of undermining decisions made by our adult children. We brought them up to be independent.
One of my daughters asked me if it would be ok to accept a date from someone much older than her as she thought we wouldn't approve, but she didn't realise her sister's partner was the same age difference. Of course we don't mind who our children chose as partners. Their own judgement has to come before ours.
If they make mistakes we will help them to pick up the pieces if they want us to.