I became a Cowboys fan in 1965, the year the team first broke even. The next two years we made it to the championship game against the Packers. The first year the Packers were a bit better. The second year we were the better team but the Ice Bowl happened. Then we lost to Baltimore on a last play field goal in Super Bowl V, which was the Blunder Bowl with record setting team penalties. Then we lost twice in close games to the Steroid enhanced Steelers including the Jackie Smith drop in the end zone. Three of those could have / should have been wins.
Tom Landry is my favorite coach of all time and Roger is my favorite player.
Landry's strengths: he was an innovative genius. The Flex Defense, the Shotgun, multiple formations, etc. He paved the way for the modern NFL.
Landry's weaknesses: he struggled to connect with his players (Plastic man), and did not or could not establish an emotional tone for the team other than a cold machine like approach. He was also too loyal to Craig Morton for too long and probably cost us a championship by waiting too long to make Roger the starter.
Landry's weakness was that he was too smart. He designed plays and offenses and defenses that the players, being made of flesh and blood, just couldn't execute.
But also there's this - people talk about the Chiefs, and before them the Patriots, getting all the calls. It was the opposite with Landry's teams. There were so many things that happened that prevented Landry from winning more SBs. Such as:
In the SB against the Colts, there was the fumble on the goal line that was clearly recovered by Manders, who was holding the ball up to the ref, but one of the Colts players was screaming "Colts ball! Colts ball!" and the ref awarded the ball to the Colts in error. A td there and the game was over.
In the first Dallas-Steelers game, Benny Barnes was flagged for pass interference on Swann, when clearly Swann tripped over his own feet (or the turf). No completion there and Dallas was well on its way to the win.
In the Ice Bowl Landry called a pass play to Dan Reeves, who was wide open for a sure td, which would have given Dallas a big lead, and in those conditions it would have been nearly impossible for GB to come back and win. But Reeves had been poked in the eye a play or two before and couldn't see out of the eye that was facing the throw, and he dropped the pass. Should have told Meredith about the eye but didn't. Not Landry's fault.
There are many more, but pointless to go on. That was the way it was. And sure, other teams have had similar things happen.
But it just shows that a few plays here and there cause a big loss, Landry could easily had at least 2 or 3 more championships, but Fate intervened.
As noted here, Landry was an innovator and a class act, there's more to being a great coach than winning titles.