I'd agree that nobody is ever 100% prepared but as a prospective adoptive parent you can be better prepared than most.
But adoptive parenting does put you into a different ball game.
My son has 'conventional' disabilities for want of a better way of describing it - he has autism and an associated learning difficulty.
To be honest dealing with ASD has been a piece of cake compared to the other stuff that comes with being adoptive family.
When you have a birth child you know exactly what's happened to them, what you ate and drank during pregnancy, what stresses and strains you were under, you know whether there are genetic conditions that run in your family.
With an adopted child you never really know, my son's birth parents claim they never drank or took hard drugs, but in truth that seens unlikely. We have no information about medical background or history. We can't be certain what happened to him in the four years he lived with his birth mum and the dozen or so addresses she lived in with god knows who.
Your birth child will never have to deal with the idea of there being another family out there, another mum, potentially siblings, issues around identity, who do they look like, where do they get their hair/eye colour from, did they inherit their love of music, sport or whatever from. You may have to deal with a whole set of issues around contact and letter box.
You may also encounter judgement from others, your family not accept a child as truly part of the family. I've been incredibly lucky with my family, but my oldest friend, who I've known since primary school, so 40 years by the time I adopted, has taken zero interest in my son. We are no longer really friends. My son has been bullied for having ASD, being black and being adopted.
In the 8 years that we have been a family, by far the most difficult thing I have ever done was support my son through two years of therapy and his confusion, feelings of rejection, lack of self esteem, and sense of responsibilty for his birth parents and whether it was all his fault.
For me, this is what sets adoptive parenting apart.
Adoption is a funny old thing, but even at its best, its not the same as bringing up a birth child. Yes of course a lot of it is just the daily grind of parenthood. But a lot of it isn't.
I wouldn't swap my life or my son for the world, but it can be very hard work.