This is a really unproductive class of response to criticism.
It's unreasonable and pointlessly limiting to restrict criticism to people who can potentially replicate the results. Also the ad hominem aspect really sours the mood.
It depends on what it is a response to. If someone says that a particular feat is no accomplishment and easily replicable for essentially anybody (not e.g. in comparison to other participants), it doesn’t strike me as too unreasonable to call the person claiming it out on that.
Sports are different from, say, someone criticizing art that way, where an appropriate response to “I could have done that” is often “but you didn’t”.
But in this case that commenter did not say "anyone could have done it". My interpretation of that comment was that the actual accomplishment is different (and lesser in terms of athleticism) from what the headline suggests. Does that deserve a "but you didn't" rejoinder?
It's unreasonable and pointlessly limiting to restrict criticism to people who can potentially replicate the results. Also the ad hominem aspect really sours the mood.