I'd say "no". Why? Premature optimization (http://c2.com/cgi/wiki?PrematureOptimization).

Consider fictional a application called Amazoon, where the "database" was the slowest piece of the app, e.g. registering a new user or searching inventory was taking ~2 mins per query. Changing the "View" layer from HTML to Angular, React, or <insert latest view-engine here> will have a minimal impact at best simply because the bottleneck is elsewhere...

Your shiny new "rectified" Amazoon app will go from 2 mins and 20 secs per query (old app), to 2 mins and 15 secs (v2.0 <- still lame, boo!).

Bad approach, bad results.

Alternatively,

1. If Bill was really smart, he would first benchmark his application and application components (app layer, view-layer, db-layer, caching, etc).
2. Identify "what" part of the system was the slowest.
3. And then fix "that" piece.
4. Repeat starting with Step 1!

Ps. I love "React" so Bill still gets points for his fix. ;-)

Depends on the app.

Bill is using one solution and forcing it on all problems, not all problems are nails that requires a hammer.

What does Bill start with? an MVC App.... in what language? How is Bill using React, isomporphically or just on the front end?

I use React and I'm happy with the results, but it does fit on my app requirements.

So, I'd not use React as a general solution for all web apps. It will always depend on the app requirements.