It’s not an abuse of language or meaning or communication. It’s a rule that you really want to be true for English but which unfortunately has exceptions. Irregardless is one of those exceptions. It’s not a word that I personally use because I don’t like it (probably for the reasons you’re articulating) but English doesn’t actually care what you or I think. Using “irregardless” as a synonym for “regardless” or “irrespective” is not incorrect.

OED calls it a “nonstandard or humorous use” https://www.oed.com/search/dictionary/?scope=Entries&q=Irreg...