It's not "old stuff is better" as much as "I'm better than you."

For a long time, that was by having sharper, higher-quality pictures. Your friend had some Kodak Instamatic and you had a Hasselblad and you could assert your dominance over them.

But nowadays, the phones in everyone's pocket take such outstandingly sharp pictures that there isn't really meaningful room for improvement. So, people now differentiate themselves by getting vintage digital cameras which are hard to find, cost extra money, break frequently, etc., so that they can demonstrate their uniqueness.