That’s one of the biggest lies told. Children will fare better in a two parent home where there is mutual love and respect. You do not have that right now so that makes it a toxic environment.
Coparenting is not that difficult. I only speak to my ex about the kids nothing else. Most is done by text and a few phone calls. I never speak badly about her to my children even though she is being a bad parent right now. I try to minimize the damage for my children.
A my fear is that right now you are still in the denial phase of the stages of grief so I’m not going to lie you have a long road ahead of you. Exercise, eat right, get good sleep and practice self love.