Somebody who comments ‘this is silly’ is often commenting from a perspective of ignorance, or from having an incomplete understanding of everything going on.
Most things are in place for some good reasons, and if you don’t know those reasons, then you might indeed think something is silly.
The correct response therefore is probably not to agree because that would indicate your own similarly relative ignorance, which is unproductive.
Instead, you should give facts (if you know them) or pivot the conversation to seek more information (yes, what is this? Why does it exist? Does anybody know?).
The three criteria of a productive contribution: is it good? Is it true? Is it useful?