Harry Dunne said:
To take it even further, it would be like saying that because a hitter can smoke a ball but happen to hit it right at the fielder for an out, that hits do not matter.
By your logic we should only use barrels or exit velocity etc. and although those metrics might paint a fuller picture of whether a hitter is hitting well or not, hits still matter.
This is a very dumb analogy. Let's ignore the fact that hitters have 550 PAs per year while pitchers have 32 GS per year for a second.
The outcome of a single AB relies on the pitcher, the batter, and whichever fielders are engaged on that single play and is determined as soon as the play is over. The outcome of a starter's game relies on the pitcher, the batters, any relief pitchers that enter the game, and whichever fielders are engaged on every play from the first pitch until the starters' last and is determined at the end of the game, regardless of when the starter leaves the game.
When pitcher A can pitch 8 shut out innings yet get a no decision because another player gave up the run in the 9th. And when pitcher B can pitch 1.2 innings and give up 7 ERs yet get a no decision because the offense bailed him out, that tells you how meaningless W-L is for an individual pitcher.
