Yes, I completely agree with you that the problems could have been addressed within the partnership. The thing that gets me the most, aside from this co-parent business, is that if that opportunity had been taken, the new relationship could've been way stronger and built on a much solid foundation. Alas, most of us don't get that opportunity in the moment.
I think that packing up and leaving, outside of circumstances of abuse, is the cowardly way out. I know I am making a judgment call there, but I truly feel that what you decide to do when things are going down the drain speaks to your character. In my case I also feel that W did abandon me - no prior notice, no nothing, and then one day BOOM - BD out of nowhere. But I know that the abandonment is 100% about them and not about you. Unfortunately, in my life I've had to face this a number of times from very close family and it was never about me.
The main reason about looking at ourselves is to truly understand who you are as a person. Most relationships, both parties caused the breakdown, even if one person decided to pull the plug abruptly. And if we look at ourselves with brutal honesty and self assess without judging ourselves, then we can chart a new future for ourselves with or without our partners. If I have learned anything from this board and life, it is that.
When people ask here about 'successful' reconciliations (where the relationship was restored and in piecing), the most common and obvious pattern is that the LBS did the following things - took accountability for their shortcomings, engaged in personal growth in professional and personal lives, walked the path of detachment and letting go, reduced contact and demolished any expectations, improved their emotional fitness, and got a life. It is about a complete mindset transformation and then following through with action.
So, that's what needs to happen. Because the outcome will always be you becoming a full human being and reclaiming your life - it's story and future trajectory. It creates empowerment and peace. I have never been at more peace in my life than I am now, and that is no small feat. For the first time in my adult life, I am excited about what my life is going to bring me. I don't recall being like this since I was a kid - full of hope.
This is completely achievable and not only that, it is a way better place to be.