Most fans can tell when players and teams are struggling. Occasionally one or two new signings can transform the fortunes of a team, but mostly teams don't play well because the manager wants the players to play in a way which they can't, or won't. We've all seen teams relegated when, with the players available, they should have done better.
The issue - in my opinion - is that most managers are ex players, and use the same motivation that was used on them, use the same tactics their manager used, see the game as it was when they played 20 or 30 years ago. It might work, but with European players and continental players, it's more likely to fail. And unfortunately, most managers are thick as castle doors, so don't think about other ways to get the job done.
There are so many stats available to managers nowadays but most managers don't use them. When a particular goalie punches away a corner, where does it end up most often? Put an attacker where it's most likely to go and maybe you can play it straight back in. Is a goalie susceptible to long shots? Is a defender regularly out of position?
The managers that succeed take a far more detailed approach to the game, on and off the field. Some players can't adapt to new ways and get moved on. Others thrive. Management now is much more than deciding you want to play 3-5-2 or 4-4-2 and tell the players to get on with it. I don't think Chris Wilder sees it any other way.