A lot of people here complains about Rails performance, and that is one of the reasons why I use the Grails - Java framework. It is not as polished as Rails, and has a few sharp edges, and it has a much smaller community which is still super-friendly and awesome. Grails however can still take the advantage of the enormous Java ecosystem. You have a library for about everything. And many of them is of really high quality too.
I have for the last five years built three successful startups with Grails, where the last one now employs 100 people. Grails has been really helpful here, as it has made it possible to move fast and add,fix,improve,break changes quickly. For my last startup Rails would most likely have struggled with the amount of data we are dealing with, while Java is hardly sweating. It is not something Grails specific, but still a part of the Grails application, that is why I mentioned Java.
My last startup, which now employs over 100 people didn't use React nor Angular either in the beginning, just vanilla Javascript. More speed, less complexity, less errors and so on. We use React today, but that is because new employees really really wants to work with. And developer happiness is really important.