React can be a way forward. But it won't automatically improve the perf. First take a look at your middware if you have decision making power on that. The slowness can be mitigated using microservices and graphQL. Without this enhancement, widget to widget, PHP/jQuery is hard to beat.
There are many ways to write react. Take a solid boilerplate like react-boilerplate. Then bolt a good dashboard template on it. Get rid of crazy stuff (redux etc)
Use Material. Write simple Functional components using hooks and tie everything together.
When you are rewriting, let go some stuff that you don't need.
Source: we are in the middle of what you want to do.
