My impression many years ago was that it’s really not that bad. I got up and running writing simple programs immediately, and wouldn’t have tried to go outside its capabilities as a simple scripting language.
Tk has been embedded in python as the GUI toolkit since at least 2.x days. It's used for IDLE, the IDE shipped with Python, and is also used for the turtle module's graphics.
Because Tcl is a very compact language, and is easily integrated with special hardware, it is a popular choice for embedded development. You'll find Tcl hidden away on many devices, including many networking products from Cisco and others, and set-top boxes including Tivo. Embedding Tcl within other software projects is of course also hugely popular, and has become the dominant control language in some industries, such as in electronic design automation (EDA) and computer-aided design (CAD) applications.
Important softwares written in Ruby for example include Rails and Homebrew.