I've been deploying Rails since v 2, and never with Docker. The only time I ever had trouble was setting up Rails dev on M1 Mac when M1 was new. In Linux production, it just worked; and pulling/building gems was less a drag than what people regularly experience in the NPM world.
To be fair, I don't use a ton of gems because I generally don't like additional dependencies unless the value is really there. So maybe my use cases have been too basic to experience the pain.
But if you just install it directly via package manager, leave alone and need to say reinstall server or something, the knowledge is lost.
I remember having a lot of ping-pong between ruby devs where they, well, didn't note down what system libs and dev package they needed, just had them installed locally at some point and forgot about, then surprise when app isn't compiling on server.
Go app which is one blob and some static file ? Sure. Java app that just needs JVM in system ? Go ahead, .service systemd file with some limits is all you need.
Ruby on Rails ? Put that radioactive shit in container, else your server will need to have a bunch of -dev packages just to compile gems and make it running (or alternatively you'd have to compile the gems on same environment server is running, which is more work than just making a container)