If you have virtually unlimited budget then keeping an over-leveled person in an overpaid position can slide if they’re still adding some value. However, it’s still better to demote them (difficult) or remove them to prevent animosity from brewing in their peers.
If you only have the budget to hire a few people, then having an overpaid and underperforming person taking up a valuable slot in your limited budget is a pressing issue. You need to get them off the team to free that budget up for someone who can earn it appropriately.
If you have virtually unlimited budget then keeping an over-leveled person in an overpaid position can slide if they’re still adding some value. However, it’s still better to demote them (difficult) or remove them to prevent animosity from brewing in their peers.
If you only have the budget to hire a few people, then having an overpaid and underperforming person taking up a valuable slot in your limited budget is a pressing issue. You need to get them off the team to free that budget up for someone who can earn it appropriately.