Let me put it another way: are there a lot of examples of other teams trying to give coaches a lot of rope and them failing anyway?
You still aren't getting this. You think this question somehow refutes or undercuts the fact that every successful coach other than Landry that has been in one place as long as Garrett has been here, has had way more success over that period than Garrett.
But to answer your question, yes, there have been coaches with long tenures that never won a SB or even made a SB. Marvin Lewis is the clear peer for Garrett to date. Marty Schottenheimer had a long run in KC where he never made a SB despite the fact he was far more successful in his first 8 years in KC than Garrett was. Chuck Knox spent 9 years in Seattle. Never won or made a SB. Another guy who was given time and was more successful than Garrett out of the shoot and still couldn't deliver.
Jeff Fisher spent 17 years coaching the Tennessee franchise. Never won a SB. Frankly had a pretty poor postseason record only making the playoffs 6 times in 17 years. But in his 5th full year, he made the SB and lost to the Rams. They stuck with him and he never delivered much of anything beyond that SB year.
Jim Mora spent 11 years in New Orleans. Made the playoffs only 4 times and never won a playoff game.
To a lesser extent, Philly stuck with Andy Reid and never won a SB. But they did make 5 NFC Champ games, including a few appearances in the first 5 years in Philly. John Fox spent 8 years in Carolina, only made the playoffs 3 times and never won a SB. But again, unlike Garrett, he had some success early making a SB in his 2nd season and a NFCCG in his 4th year.