I understand the broader point you're making about poverty, vulnerability and whether a woman’s choice can ever be completely free when she has so few alternatives. But I think there is still a fairly significant leap between that and saying that economically empowered adoptive parents have a moral obligation not to “remove the babies of the poor or vulnerable”.
The adoptive parents didn't make you poor or vulnerable, and they didn't create the circumstances that led you to place your baby for adoption. Unless they coerced, pressured or otherwise exploited you, I'm not sure it follows that accepting a baby who needed a home makes them morally responsible for the inequalities surrounding your decision.
You can look back now and feel that you needed more support, or that adoption wasn't what you emotionally understood yourself to be doing at the time. Those feelings deserve to be taken seriously. But that doesn't necessarily mean the people who adopted your baby wronged you.
I also think there's a difference between saying “vulnerable women need better support and genuine alternatives” and saying “therefore people who adopt from vulnerable women are participating in exploitation.” The first doesn't automatically establish the second.
Ultimately, if your understanding of the pregnancy as “surrogacy” was a way of making sense of relinquishing your baby, I can understand why that framework felt meaningful to you. But it doesn't create obligations on the adoptive parents that they never agreed to and, presumably, didn't know existed.