Mostly agree with you, but at some point, if the evidence piles up that Dak will never get this team to the SB (as far as his quarterback play is concerned) so eventually despite "consistent playoff caliber teams", if your goal is to win it all you'll have to get rid of Dak.
For me, that point was reached even before this latest poor playoff performance, though I will say even if he had played very well in this last game, Dallas would still have lost. The Packers went down the field in their first 2 drives to tds, ran all over the defense and generally just played much better than the Cowboys. Dak's late point surge was meaningless, the Packers were obviously in prevent defense mode.
But throwing good money after bad is not a good plan, either. Even if the lack of SB or NFC championship game appearances isn't' Dak's fault, at some point you have to make a change, regardless. Being stuck in a rut is not what I want in my team....