I know other people question that sometimes, and suspect we may be getting "set up" here by someone trying to be clever.
To try to take this seriously for a moment, and use your words I doubt whether this is necessarily the way it should be:- "We would think that there would be 50/50 all the way until the child turn 18 or 21 year of age."
If you would be happy to have some input into your child's life, regular contact/access perhaps and the other side could be persuaded to agree or even lent on a little by the courts - how does that sound to you? I don't expect your ex. partner/wife to put your child into the way of any harm, but if you want to try to be a responsible or fit dad then you shouldn't be dismissed without consideration. Maybe you will have a bit of proving to do before any court will listen to you though. I not sure whether I should ask but did you have a meaningful relationship with the mother before your child was born (say lasting over 12 months)? I think that makes a difference to the maount you might care about your child.
I had my relationship ruined with my daughter by a never ending stream of negative comments. I'm sure you are subjected to something similar as well. Everything from her mother telling our daughter I stole her Easter eggs, to "your father never does anything interesting during contact visits only taking you (our daughter) to the homes of old people" (keeping in touch with elderly relatives isn't right in the eyes of a hostile ex. and court welfare people very often - you only have to see how badly grandparents are treated to see their attitude to the aged).
That's about all I can tell you. I hope you are genuine, and please acept my apologies for doubting you if you are.
ATB, Graham