TCL stands for "tool command language." In terms of non trivial tools that have been built with it there have been several. AOLServer, MacPorts, tons of CAD and engineering software. There's a whole wikipedia category just for this:

https://en.wikipedia.org/wiki/Category:Free_software_program...

Aside from that there was Tk which was used to create many UIs in an era where scripted UIs were otherwise painful to create and maintain. A prominent example here is 'xconfig' from the linux kernel.

Like any good environment a little bit of practice with it can see you overcome it's apparent shortcomings and see you producing reliable and useful software in far less time that you might have in a more traditional way.

Programming is about trade offs. It's not a checklist of "good ideas."