So many myths here about adoption.
It’s entirely possible to adopt babies (eg under a year old), I know a number of people who have done so over the past few years.
Difficult childhood experiences, poor mental health, single parenting, debt, limited social support, being in receipt of benefits, high BMI, etc etc aren’t in and of themselves barriers to adoption. It’s not about what’s happened to you so much as how you’ve come through it, whether you’re financially solvent, a functional adult and likely to have good enough health to see an adopted child well into adulthood.
Children placed for adoption in the U.K. have experienced some level of trauma - even if that’s the experience of moving from foster care to adoptive parents or some form of pre-birth trauma. Some children will be massively impacted by their experiences and struggle throughout their life course, some won’t, never underestimate the impact of being in a secure, loving, caring environment in recovering from trauma.
Being able to care adequately for one child doesn’t mean the decision to remove an other child/children was the wrong one. There are lots of reasons why one child may need to be removed while another can be cared for by birth mum, mum may be able to cope with one, but not more than one, one child in the family may be scapegoated, one child may have a particular meaning to the birth mum (eg a reminder of an old/abusive relationship) which results in neglect or abuse etc.
Difficult to place children aren’t necessarily difficult to parent. My two DC were considered difficult to place - they were older in terms of adoption (aged 4 and 6 at the time), there were some developmental issues and they have attachment difficulties understandably. They are an absolute joy, they light up my world in a hundred different ways and are thriving at home and at school. They actually aren’t difficult for me to parent. There are challenges, yes, and it’s very hard work at times but they aren’t difficult children by any means.
And my DC are my DC. I’m not minding them for someone else, holding a place for birth mum, looking after them or depriving their birth family of the opportunity of caring for them. They are my children, I love them fiercely and deeply - they return that love in bucketloads, we are a family.