Comment by Glyptodon

For early stage startups using react easily multiplies your required engineering man hours to get to market by a considerable factor. The biggest pro is probably that it pairs nicely with GraphQL, which, in many domains, is nicer to work with on the back-end compared to other options, but is also decidedly unfriendly to most options that minimize front end dev hours.

Point being, not to say no to React, but that if your org's size is small enough that you don't truly have multiple teams, you probably get way more mileage and output per $ using tooling that takes after Phoenix Live View, whatever that is - Hotwire, Livewire, etc.

On the other hand, you may expect that having more distinct BE/FE will pay off because of being able to have separate teams, easier to fit in a mobile app, etc. This has some truth, but it can easily turn into taking away from product focus too early in a company's lifecycle.