Tmux comes with the ability to script it, intentionally and by design, and it’s very straightforward and simple to open several windows that launch commands in them. Tmuxinator doesn’t reinvent that, and it does add another dependency, and another layer of options and flags and project syntax to learn.

The suggestion to check it out is great, but saying that people who don’t use it are reinventing it is a tad heavy handed. There are good reasons and legitimate scenarios to keep it simple with tmux scripting alone.