3. Signing free agents who are on the decline
One of the things that always bothered me under the tenure of general manager Kevin Colbert was Pittsburgh's willingness to sign free agents or make low-level trades for players who were already on the decline. The Steelers did this with Myles Jack. Despite coming off a horrific year with the Jaguars, Pittsburgh rushed in to give Jack a big contract the moment he became available.
They did this a year later with Patrick Peterson. Yes, both players were good at one point, but that ship had already sailed. The rest of the league understood this, but somehow, Tomlin and the Steelers naively believed that there was still plenty of tread on the tires.
This has been the case with many of the free-agent decisions they have made in recent years. The Steelers have signed some high-profile names who were no longer high-profile talents. A lot of times, we can trace this back to Tomlin's interest in some of these players during the pre-draft process (CB William Jackson III is another perfect example).
The Steelers need to be able to separate their love for a particular player from the player they are actually seeing on the field. It was easy to see why some of these players who were past their prime or had injury histories didn't work out. They can't keep falling into the trap of signing free agents who are on the decline.