Development hell is caused by management hell and can't be fixed with person-hours. It always requires new managers. Management will often swap out devs trying to fix it, but I've never seen that work.

Finishing a 9-mo project a little late isn't a great sign. It should at least result in a usable beta because it's such a long timeline. There are many months to change course and narrow the features in a smart way.

2 years for a 9 mo project is a garbage fire. It was in development hell a long time ago.