Shades, I think that we have a tendency to overlook what was probably glaringly obvious for some time.
I am in a similar situation. H was never that involved with the kids.
Out of everything that he has done, this has been the biggest disappointment - I always thought he would be a better dad.
Now friends are telling me that they noticed this a long time ago. And, honestly, so did I. I spent more time with the kids trying to make up for it, and probably ignored him in the process.
And I know your friend was just trying to be gently honest with you, but IMHO you can't be nice and be a husband stealer.
