Something that people said a lot during the mid 2010s when trying to relay the obviousness of a point, often with a snide, flippant, or factieous tone or attitude. As of 2020, the only people still using such a dated term are basic bros and housewives who shop for their evening apparel and their husbands' professional wear at Target.
When saying "Just saying" any where in a sentence, the beginning, end or the middle, it justifies your sentence as redundant, but in your mind you think its concise.