You might think you are "unimportant" and maybe at your company that's true. Looking at it less cynically you could also be reliable, capable of parsing and improving code, and more familiar with a wide variety of code styles. These suit you well to this job and being a janitor often pays really well. Often times as I advanced in the ranks I spent more time modifying other people's code than starting something from scratch.
You don't want to be learning new tech stacks all the time. If that's your personal hobby - great. But these stacks come and go and collecting N number of tech stacks to throw on your resume won't make you any more desirable to a new position down the road that requires senior X or staff Y and you've spent so much time in varying tech stacks you're not at that level. At the end of the day people WANT "boring" engineers. They're reliable, predictable, and knowledgeable.