Today's Rails has https://hotwired.dev and it's built-in. I've used it on quite complex UIs and for the life of me I don't believe React would be so popular in new projects if people knew how good this was.

There were some hard problems related to legacy systems that made it hard to provide the best possible DX; eventually the influx of React devs was too strong to hold - adoption started in 2020 IIRC.