Not aggressive. I am simply stating my position based on thirty years of running a range of tech businesses. Others can do as they wish. And they do. And the overwhelming majority of software developers have exactly zero time or interest in deviating from their work to mess with tools source code. Some percentage will customize via macros and relatively minor scripts but virtually none go so far off course as to spend non-trivial time hacking source.

Language such as "exactly zero", "dork around", "mess around" sounds aggressive, as if people who decide to hack on their tools were beneath you. When you say "utter waste of time" on people who do enjoy working on their vimrc or init.el or whatever, it sounds like you think the person themself is a waste of a person. When you mention how many years you have, you sound pompous, as if you were stating your opinions as facts (years of experience can't be wrong!).

It sounds aggressive even if you don't intend it to sound that way. There are ways to other ways to express your opinion without sounding this way.

Here, let me try to show you what I mean:

"I am not interested in modifying my tools. I would rather pay someone else to do it. If you are spending time modifying your tools, then that is time that could have been better spent on another task. I have many years of experience, which have convinced me that the right way to spend your time is on your product, not your tools."

Note the lack of dismissive language such as "absolutely zero" or "exactly zero" or "waste of time" or "I am simply" (this last one is another attempt to present opinions as facts).

You are going out of your way to ascribe meaning where it doesn't exist. Not sure what to say.

When I say "I have exactly zero interest" it means exactly that. If it offends you the problem isn't mine.