Allow me to tell you why I, a lazy good for nothing millennial, usually forgo cereal for breakfast.
My day begins as I wake up, shower, and make myself look nice to tackle a day of classes and labs that move me ever-so-slightly closer to my bachelors in zoology, tasks to complete as a leader of a large and influential student organization, studying, looking for jobs, trying to find a new home to move to, and keeping up with my various friends (not to mention my hobby of moderating this very forum and roleplaying therein). With so much to do, I often don't have time to get out dishes, cereal, milk, etc, sit down to breakfast, and clean everything up afterwards before I run out the door, so I opt for a piece of fruit and/or granola bar instead. On days when I do have time for breakfast, I tend to opt for oatmeal or an egg sandwich, because if I'm going to take the time to sit down to an actual meal involving dishes and cleaning and such, I should probably make it one where I actually put something nourishing in my body.
So there you have it. The secret behind our millennial "laziness" is that we're in fact doing a million different things and need to get the most out of our time. Honestly, a lot can be said about this article, how it provides no hard data even in what it cites and how it's giving the same weak argument that countless articles give these days, but at the end of the day it's an article in which someone set aside time out of their own life to call an entire generation childish while complaining that cereal doesn't come with toys anymore and that they can't eat a certain cereal because it reminds them of a "weird fandom", and that's really all that needs to be said.