Success is relative. A handful of NFL teams would be disappointed by anything short of a Super Bowl LIV win, like the Chiefs, Patriots, Rams and Saints. The second tier of teams would set their minimum at making the playoffs. A third tier might simply want to compete for a playoff berth.
There's a fourth tier of teams that might set their sights even lower. While they likely harbor dreams of playing competitive football in January, their realistic goals for the upcoming season have more to do with developing young talent or finding a solution at a key point of weakness on their roster.