Two years ago, I started a new company, and decided at the outset to avoid using any heavy JavaScript SPA framework. We stuck to simple server-rendered html and only use progressive-enhancement style JavaScript.
Our app was fast, and simple, but it also came at a cost: we were limited in our ability to take rich UI elements off the shelf with an npm package. We had to do a lot more work to provide a rich user experience. Everything took longer, and the user experience was worse as a result. We cared, but sometimes you don't have time to carry through.
The company failed, and I don't think react would have saved it. But I can tell you first hand that righteous adherence to "simplicity" didn't help either. It's always a trade-off.
I feel like there is some context missing in your story here. There is a lot of middleground between heavy SPA frameworks and creating everything from scratch. More importantly, I am left wondering what sort of functionality was your team trying to build that requires that much interactivity? At least that is what I assume with "rich user experience"?
Our app was fast, and simple, but it also came at a cost: we were limited in our ability to take rich UI elements off the shelf with an npm package. We had to do a lot more work to provide a rich user experience. Everything took longer, and the user experience was worse as a result. We cared, but sometimes you don't have time to carry through.
The company failed, and I don't think react would have saved it. But I can tell you first hand that righteous adherence to "simplicity" didn't help either. It's always a trade-off.