A child with one loving parent is better off than a child with any number of disgruntled uninvested parents.
A single mom who goes through all the effort that IVF requires is someone who REALLY wants children. That's someone who will appreciate the gift of parenthood and make sure that they don't waste it.
I'm more concerned with the children that were forced to be born against their parents' wishes. Those children will be seen as a burden that was forced upon their parents. They will be resented, and more likely to be neglected or abused. They will grow up never learning what love and kindness is, and they will take that hatred and spread it into the world, or give up on themselves and turn to drugs, or an abusive relationship.
Thankfully, my wife and I were both open to seeing single parents. Now we are married parents with more kids than we started with!
If you mean as a person without kids, I have a tip: YOU SHOULD NOT BE MORE IMPORTANT THAN THE KID.
That's not too say that you aren't special or important, it's just that the kid(s) are children that rely on their parent to exist. That's a big responsibility, and it needs to be respected. You're a grown ass adult and you can take care of yourself. If you can't deal with your partner not restructuring their whole life around you, then stay away from people with kids.
You don't need to shift your own priorities and make their child your number one, (maybe if things go well in the long term, that will happen on its own) but, if you go out of your way to at least be friends with the kids, or learn a little bit about them, that's going to score a TON of points with the parent.