I'm doing exactly this now ... the problem is multiple iterations of trying to set an architecture and a pattern to where things go. The architecture presented, if it was to be implemented that way would have been perfectly fine.

Now there are 3 iterations .. with 3 different patterns of what would be a state container, UI business flows split across 3 layers (data access/api, business/decision , view models) and view models (NOT VIEWS) sharing state.

What also doesn't help is the tooling is close to non existent .. I got so used to webpack / lib(framework) dev tools / hot reloading / all in 1 dependency management / intellisense

If your predecessors were indeed total hacks at programming, you can get all of the above. But it's a dubious pleasure. My head sustained a lot of scratching and smacking and my face was over-palmed.

It's not that they were total hacks. It's that they fell into the 1 standard deviation of the normal distribution that made them an average developer. Average devs produce the status quo, which is "software that works but that everyone complains about having to maintain". In my experience people with solid framework design and system architecture skillsets invariably fall into the top tail end of the distribution. They aren't like other developers. And they're rare. They can and often do get dubious pleasure out of making old code new again.

Sometimes a very dubious pleasure. I work at a company where another product team decided to rewrite the entire product from Angular 1 to Angular 2 because it was so much better. I was shocked and dismayed, but didn't say much because I didn't feel like starting a fight I would lose, and it would suck me into a project that wasn't my primary focus.