I think there should be some incentive for that, like make those kinds of comments a spotlight or something. Maybe make a community called “late replies” that showcases the best such replies, or have a rule saying they grant free karma (in Reddit’s case).
What a horrible name for “people responding to a thread that is older than a mayfly”.
Suggesting something a few months old is “dead” is especially churn-y; like “Ahmahagawd, that thread is, like, SO last-heartbeaaat”. Ensure the voice dissolves into an indolent vocal fry for best effects.
Its a fairly established internet term and/or culture. This isnt a “zoomers have no attention span thing”, its been a thing since the dawn of the internet.
Life moves on.