But before you leave write a very well considered and professional memo and send it to the CE/board/exec team, offering to meet with them as well. Keep it internal, and leave it there.
I would aim at communicating three things:
1: That a problem exists at your level, and give three examples of how this manifests. Focus on how things work rather than on people and personalities and the overall implications for the project and organisation.
2: Your understanding of the root causes of the problems. For this it's best to canvas other people but make sure the conclusions are your own and not blamed on others. Focus on causes that are not people but processes/structures that have et the organisation up to fail.
3: Your recommendations for the senior exec/board etc. Again I would give tangible things they can do that do not involve individuals, such as immediately de-scope the project, bring in certain external help, separate out this department and that and so on.
If they are smart they will meet with you, and even keep you on in a role where you can help make changes. I suspect they will not, but at the very least you will have tried, and they will have evidence that they should not ignore.