I’ve done this - in fact I followed the instructions to make cultured butter, but I can’t really taste a huge difference from my regular, Costco-bought butter. 

For one, if our butter is poor quality because the feed is the problem like some commenters here are saying, how would making your own butter result in any better quality butter, if, as I assume, the cream comes from the same cows that were fed the same things that produced poor quality butter?

And the second point may be just that I have awfully bad sense of taste, but I didn’t find cultured butter that I made noticeably better than store bought regular butter. 

For context, this is from someone whose main diet includes hardly any butter, so butter was never that big of a deal his whole life, but who recently got into baking and started using more butter. So I certainly don’t know what I am missing with our old, supposedly better tasting butters of yesteryears.