I would say that stamp collecting is the ultimate collectable and its a natural fit for Millennials.
In general stamp collecting can be an endless lifelong treasure hunt. It sharpens the mind - combining aesthetics with a tangible study of history. In a sense philately may be more important now than ever. It could also prove a superb investment if purchased wisely - and one does not necessarily need alot of space to store the collection.
Importantly there are many millions of examples available in the marketplace - at all price points - young collectors can happily start with penny stamps and eventually work up to world class rarities. At all levels they can be displayed like a fine art collection.
And we would probably agree that classical Mexico may be among the most interesting, beautiful and complex countries to collect in all philately.