Earlier quoted context omitted.
I think you should form your opinion after hearing what Cantonese (and other regional "dialects") sound like. Then you should be able to appreciate just how close the Northern speech is to Standard Chinese.
I'm not sure why you think I don't know what other dialects sound like. I know what various languages and dialects in China sound like, and am most familiar with Cantonese, Sichuanese, Hunanese, Hakka, Shanghainese, and Yi. Yi sounds positively African and is not a fair comparison, given that it doesn't even share the same writing system and is probably an actually completely different language family. Sichuanese sou…
https://en.wikipedia.org/wiki/E_language
It appears to be a Tai Chinese creole or mixed language (like a creole but without the massive simplification in grammar).
Yi(Loloish) is definitely a different language family though that wouldn’t stop people writing in Mandarin if they really wanted to. Vietnamese, Korean and Japanese were all written as if they were Classical Chinese to greater or lesser extents until relatively recently.
https://en.wikipedia.org/wiki/Loloish_languages
I’ve heard Sichuanese described as Mandarin without tones. All of Sìchuān speaks different forms of Mandarin for the same reason Manchurians do, recent massive resettlement, though not as recent as in 东北.