Basketball is the sport I follow, though I agree Baseball has gone further down the stats hole than any other sport.
The thing about sports stats, or at least basketball stats, is you can start with a huge amount of historical data, and ask a huge array of experts from players to coaches to general managers to sports casters and journalists and retired players and similar experts in the field, and say "Who do you think was a great player for their era?" and get a fairly universal list of agreement from people on who was great.
And then you can craft a stat which reflects that consensus opinion, and which also functions for current players.
Like for example a basketball stat like Player Efficiency Rating. Is it perfect? Absolutely not. In fact, it lacks for defense, and you need to combine it with a defensive stat tool to get a better picture. But does it function as a decent tool which, when run against historical players and current players, comes out pretty close to consensus of opinions of experts on who is good? Yes, yes it does.
Which means it's a useful measurement tool, even if it isn't perfect.
Much like DPR. It doesn't reflect all aspects of the game, but it doew reflect enough of a very meaningful element of the game that it shouldn't be derided by people as not useful. Yes, of course it does not reflect the contributions of a stun, a bardic inspiration, a charm, and a speed reduction on a foe. But it does reflect a meaningful and measurable aspect of the game and so has it's uses as a tool.
I don't think Treantmonk at all used it as a universal measuring stick in his video, nor did I in the post I made about monks sucking. It was used in one aspect - the offense section. And Stun had it's own section, as did movement, and defense. So I think it's a misrepresentation to imply it was being used as a universal stat improperly. It was correctly applied - to offense, as a measuring stick, without ignoring stunning.