I struggle with this too. On the plus side, the devil you know is often better than the devil you don't know, and anything new will require re-learning a lifetime's worth of muscle memory. It's also nice to know that your bash scripts are going to be hyper-portable and will still work even many years later. The muscle memory is also real. However it isn't great to be constrained with unsightly code for sake of extreme backwards compatibility. I've found a nice balance personally where I use ruby if I need anything that bash isn't good at, but it's never a perfectly clean split.
> It's also nice to know that your bash scripts are going to be hyper-portable
Doubt. I'm up to my neck in bashisms, and I require the very latest bash on top of that.
The -p flag for source landed in bash 5.3.