Was watching Bron/The Bridge some time ago. Danish sounds like gibberish indeed, but then again "We hebben een serieus probleem" was a meme a little while back.
Dutch and Danish share heritage via Frysian and Saxon (English) heritage. IIRC the Frysian lived among the whole coast of North Sea from Holland till North-West Germany, and then enclaves in Denmark, too.
Dutch is a Franconian dialect though? They just didn’t go through the consonant shift like their cousins in the Rhineland. It isn’t really that closely related to Frisian or Low German and even less so to Norther Germanic.