2016 Twins had 6 current/former SS (Dozier, Escobar, Plouffe, Nunez, Polanco, Santana (7 if you count Sano)) and 3 current/former CF (Buxton, Santana, Kepler (5 if you add Rosario and Shafer) and lost a Twins record 103 games. It's a fine line to be able to play these positions, and to actually be good enough to be a MLB starter at them.
Growing up, most MLB players are the best players on their team and played either SS or CF, and probably pitched. Most of these kids that get drafted get moved off these positions not because they aren't athletic enough to play there, but because the game is much faster moving from level to level through college or/and MiLB.
Most of the Brewer players you are referencing, other than the starters at these positions, are below average when compared to their MLB peers, but are good enough to be used to fill in for short periods when needed. Not every team can target these types of players and be able to develop them to be successful at different positions (or buy into switching positions for the good of the team), whether it's due to coaching, the player's ego, or the fact that the player is just not that good (or some combo of these), we have seen this with the Twins many times.
A team needs bona fide starters at most positions, a team of utility type players will not be successful long term. Getting coaches/managers and players alike to believe/buy into this is the big problem.