Maybe it should be more recognized that what the quote "a language is a dialect with an army" means is that borders of nations don't coincide with borders for languages, or put more simply, it has such two meanings that, there are languages that are realistically just weird accents on one another, and one "language" that are realistically two or more.

I have some confidence with dialects of my primary language(not Chinese) within ~150mi of where I am; beyond that, mutual intelligibility with local dialects isn't guaranteed. Yet, those dialects are rarely considered(including by speakers) to be separate from the standard. They're just local accents. That aren't even intelligible to city dwellers.