It's basically like shell scripts, and really only useful for running shell-like commands. You don't want to do anything complicated with it, such as any direct data processing. I mean, you can, but your code is not going to be readable. As a Cadence Applications Engineer, I had to decode so many customer TCL scripts, some tens of thousands of lines, to figure out what they were trying to do. It's not fun.

As a language, Python is the correct answer.

And now, Python just has so much more widespread support. You can get any library you want in Python, with its millions of packages available. Want to do some AI processing on your schematics while printing out a graph? There are all sorts of libraries for that. You can't get that in TCL.