I don't think it is difficult, just a waste of time (not rails specifically). If I'm already spreading myself too thin on ~20 technologies, adding N more doesn't help.

At some point (different for everyone I know) it pays to focus on a few things and get to the next level with them. I've already got a good job, but it would be nice to get "poached" once in a while. Fewer silos in the industry would help alleviate the hiring problem. Wishful thinking, I know.