I’m a writer. I was going to be an English teacher, but I balked after shadowing a few teachers as a junior.
Also, language is living. If enough people use irregardless, it becomes part of the language. There are many examples of these words making their way into our lexicon.
People are always up in arms when a word like bling or YOLO is added to the dictionary. Merriam didn’t decide that. We, as a culture, decided that. Same with irregardless.