I think 50-50 can be good as long as both parents are committed to making it work and do the necessary to make sure it does. And the child or children are happy with it. This is not always the case.
In your particular case OP, I think your ex should be seeing your DC a couple of times during the week after school and also covering half the school holidays. That does not mean just taking them on holidays but having them stay at his home, working out and paying for the child care if he still has to work.
Being a good dad also involves making adequate payment for DC, not the bare minimum of CMS. Does he buy everything they need at his place or do you provide it? Does he offer to contribute to after school activities or any childcare needed so that you can both work full time?
Being a good dad also involves knowing your child. Knowing their friends (and facilitating play dates and parties during his time), knowing what they are doing at school, helping with homework if they get it (rather than leaving it all to you), knowing their medical history, offering to deal with dentist etc rather than leaving it all to you (he could do this during school holidays - same with hair cuts, uniform shopping etc).
You might not think that 50-50 is appropriate but everything I have listed in my last 3 paragraphs should be happening if he is an amazing dad. Otherwise he is barely adequate.