I think you've way undersold Tom Landry.
Quite a bit in fact. No one saw what Tom Landry did in Chuck Howley. He had been considered a bust for the Bears. Was completely out of football in 1960.
Rayfield Wright was drafted as a TE. Landry saw him as an OT.
Mark Tuinei was a DT at Hawaii. Landry moved him to OT.
Landry saw Todd Christianson as a TE. He didn't and wanted to stay at FB. Al Davis agreed with Landry and Christianson became a great TE.
Drew Pearson was a QB at Tulsa his first 2 seasons. In fact he replaced Joe Theisman as QB of his HS team. Though undrafted Landry saw something in him immediately.
In addition to inventing the Flex Defense it was Landry who resurrected the shotgun formation from the archives of Red Hickey and made it the most efficient 3rd down tool in the NFL. He saw in Bob Hayes a way to spread defenses so thin his teams could practically score at will. It forced other teams to create Zone Defenses to stop Landry's schemes.
Every Hall of Famer of the Landry era does credit him with making them better. Bob Lilly, Roger Staubach, Mel Renfro, Rayfield Wright, Bob Hayes, Tony Dorsett, Randy White, and even Lance Alworth, Forrest Gregg, and Herb Adderly, who were famed in other arenas credit him with teachign them things they did not know and two of those guys played for Lombardi, one for Al Davis. Not to mention a guy like Mike Ditka who played under Papa Bear George Halas but coached under Landry as soon as he retired.
Landry's coaching tree is as impressive as any out there. In addition to Ditka, Dick Nolan, Dan Reeves, Raymond Berry, Forrest Gregg, Gene Stallings. Each will tell you Landry's influence on them was huge.
Bill Parcells has admitted that many of his coaching philosophies came from studying Landry. Bill Belichick routinely asks former Landry players for insights into the man.