With web applications, value gained vs. money spent isn't exponential, or even linear - the gains are often diminishing. Getting from 80% valuable to 100% valuable doesn't require an extra 20% of development spend, it often requires an extra 100% or more.
Our industry is lead by hyper-profitable tech giants, for whom spending this additional money makes sense. A good example is Meta (Facebook), where React is used to build advanced front-ends, delivering maximum revenue for the company.
Round trips and progressive enhancement
So, next time you’re building a new web application, consider the economics of your approach and then proceed accordingly. More often than not, you’ll find you can create a high quality production-ready product using just HTML & CSS. From there you can progressively enhance with something like React where there’s clear value in doing so, safe in the knowledge you’re not going to be turning customers away, or spending more of your company’s money than necessary to deliver a great product.