Let's take some non-human examples for comparison. Just about every good military strategy produced when your grandpa was young is, objectively, junk when compared to the state of war today. But just about every good piece of music still holds up - it might be different from good music produced today, but it's not worse. Your grandpa probably did mathematics with the help of books of log tables and books of mathematical instruction. The former are thoroughly junk, being at best as useful as a calculator (or calculator app) but much heavier, and at worst bearing typos; the latter are every bit as useful now as they were back then.
Describing something from a previous generation as "junk" does not convey the belief it is old - there's a perfectly good term for that, "old." It conveys the belief that it is junk.