Every programming language you learn increases your understanding as a software engineer. Every tool you are capable with increases what you can do with the software you write.
Video games don’t exist in a vacuum. Need servers for your multi-player game? Need a database to store player data? I can create all of those things - but I won’t be using Godot to do it.
If you poke around these forums you will find examples of people who are leveraging other programming languages to do things Godot can’t. This page has a list of projects which offer support for other languages in Godot:
While it is fine to say you want to focus on Godot for now, saying you won’t look at another language because you want to focus on games just highlights your lack of understanding of what actually goes into creating software.