If you did write your own argument parsing code, then yes the choice to commit to that was incompetent, barring some extraordinary situation.

I don't think it's controversial or insulting to say so in the least. It's a solved problem in every major language and most fringe languages. Spending time re-inventing it is just obviously wrong.

It's not insulting or judgmental to say that it's wrong. It's just a fact. I do not understand being offended or angry about my statement of that fact. If we're talking about what is effective engineering and what is not, writing your own argument parsing tool for actual business usage (as opposed to doing this as a pedagogical side project or something), without evidence of some exceptional corner case, is ineffective engineering. It's practically the definition of ineffective engineering.