The rebuttal to this is simple: Symphonies aren't albums. Only actual albums are in scope for this list. The modern album as a musical concept is pretty recent and only dates back to the early 1900s at most (so roughly a century old), hence everything on this list is younger than that.

Symphonies are sheet music. An album is a recorded/edited collection of specific performances. There are for sure lists of the best symphonies/classical music of all time if that's what you're interested in, but that's not what a best albums list covers.