I have been on SPA projects and I have made SPA's myself as well.
If you want speed, agility separations of concerns, MVC is the way to go. Most of the things you said are MVC and SRP, it has nothing to do with SPA, this is what I have been trying to explain. SPA stands for "Single Page Application", it doesn't specify anything beyond that, your code could be utter garbage with everything mangled together, and it's still technically a SPA. MVC on the other hand does specify how to organize your code.
I think the problem here is the SPA terminology itself and the way it's being used and marketed.
If you want speed, agility separations of concerns, MVC is the way to go. Most of the things you said are MVC and SRP, it has nothing to do with SPA, this is what I have been trying to explain. SPA stands for "Single Page Application", it doesn't specify anything beyond that, your code could be utter garbage with everything mangled together, and it's still technically a SPA. MVC on the other hand does specify how to organize your code.
I think the problem here is the SPA terminology itself and the way it's being used and marketed.