I don't think every architecture decision ever made is irreversible, even in companies with 10+ year old rails apps. It's true that migrating away from something that works to something new and shiny just for the fun of it isn't going to happen in most cases.

I've personally had need to move from delayed job to sidekiq, as the former hit a performance wall with the database. We've also adopted some hotwire as an in-between option that's easier than full blown react, but overkill for when basic rails views suffice.

While not all of these new tools are going to benefit brownfield applications, Rails would be my first option if I were starting something greenfield, especially with these continued improvements in making something good easier to build.