The goal of an NFL general manager is to construct a roster of players via free agency, trades, waivers, and the NFL draft to assemble enough talent that can compete with the rest of the teams in the league in pursuit of Super Bowls.
For every NFL roster, there are often specific weak points as certain positions where the team may have borderline starting talent or a bunch of options that just don’t move the needle. It can be nearly impossible to have zero weaknesses on a roster given player salaries and free agency, but teams must do the best they can to build up those weaknesses, so they aren’t exposed during the season.