What monumental mess up? JD couldn't easily kick to touch because Sinckler was in the way, Sincklers great effort pressured him into making an average clearance. Ford, followed by Farrell, then had the ability to put in 2 perfect long passes giving Daly the space. England's execution was spot on. The only reason JD was in a position to make that kick is because Williams was allowed to play the ball off his feet (yellow card?). It was the Welsh who then chose not to run another ruck to give Biggar time to make the kick. It was GD who chose not to take the pressure on himself and box kick. It wasn't that awful a kick either, from within his own goal line he cleared past the Welsh 10m line. It was the Welsh defence that didn't then work hard enough to get in position, and it was English skill that exploited that.
Why should the activities of the last 6 minutes be any more significant than those in the first? Or those in the middle? If Farrell had made the correct defensive read and stopped Williams scoring? The game is played over 80 minutes, and over 80 minutes the Welsh team were not the better side.
Wales' team made multiple bad decisions in those last moments, from GD, to JD, to Roberts, to Cuthbert, and many of those decisions/plays were heavily influenced by what England were doing.
And at the end of all of that, even if you just want to put it all on JD's kick, then JD is part of the Welsh team, and if his decision makes the Welsh team worse, then the Welsh team is worse.