Managers are doing a good job when both the teams they lead and the individuals they manage are thriving.
Simply stated, teams thrive when they consistently deliver quality products or services while staying within budget. Individual team members thrive when they’re advancing in their careers, learning new skills, showing initiative, taking on additional responsibilities, getting promoted, and adding value to the company.
If a team is getting its work done, but the individuals on that team are not developing professionally, then the manager in charge of that team may not managing as well as they could be. Perhaps they aren’t coaching employees, clearly outlining expectations, or addressing under-performance when it arises. That’s worth bringing up with them when discussing their performance.
Keep in mind that managers can be only as good as their resources and support, though. If a team has no time or budget for professional development, the manager may not be to blame when their employees seem to be stagnating in their careers.