Ohhh man... you couldn't have picked a better controversial topic lol. Abortion, cloning, and euthanasia don't even compare to the power of the generation wars.
Anyway, here's my opinion.
As we age, our opinion of those who are younger than us changes. When we are young, our stupid decisions seem normal to us, and we aren't bothered by them. As we age however, we realize just how odd the newest generation actually is, without realizing that we were the exact same just a few years prior. Basically, you thinking that "the maturity of those born in 2000 and above has dropped considerably as the years go by" is just the result of your age increasing, and the age bracket of youth observed stays the same.
One thing I do hate about the 90's-00's debate is the stupid posts on the internet. I think that 90's kids have a massive superiority problem, and they need to realize that a fun childhood was not exclusive to those born between 1985 and 1995 (because really, a kid born in 1999 isn't a "90's kid"). Now, as someone who was born in 98, I don't think that I'm a 90's kid, but I don't really care. I recognize and have used all of the things in the "you only remember this if you were a 90's kid" posts, and I had fun doing so. I don't actually think that there was much of a difference between each generation. Really, if kids from the 90's had the technology of today, they'd do the same as the kids now do. If the kids now only had the technology of the 90's, they'd still have the same amount of fun. With technology in mind, I think it's safe to say that technology has greatly influenced people's perception on the new generation. I mean, YouTube and Facebook is everywhere now. Those who were born in the 90's can use it to connect with each other, as well as broadcast the stupidity of the new generation (who can't yet use the technology themselves). Basically, I think that without the internet, the 00's kids wouldn't be so picked on, and the 90's kids wouldn't find themselves so superior.
On the other hand, most of my friends are female, because I despise the boys in my grade. All they seem to do is talk about parties, girls, and drinking. They disrupt class, and they don't care about their futures. I'm not saying that there isn't girls who do the same, and that there is no decent guys at my school, I'm just saying that I'd rather hang out with those who care about their future and what's going to become of the world. I don't like a lot of things about my generation, but I wouldn't say that any others were any better.
Edit: Just noticed, I went on a tangent. Damn it.