This is an oft-quoted fact, and it’s true that modern brussels sprouts are less bitter, but that’s far from the whole story. The popular preparation used to be boiling or steaming, and many people still find that gross with modern varieties. But over the past 15-20 years, frying or roasting them, and topping it off with things like bacon, parm, balsamic reduction, etc. became the standard preparation, and this is just a way more delicious way to cook them (for most ppl). I’d assume this makes a massively bigger difference than a reduction in bitterness.