I would suggest asking for an objective evaluation of an OO design may elude you. You can learn amongst other things
- SOLID principles
- Dependency Injection patterns
- More general design patterns ie GOF.
- Domain Driven Design
The design may express certain attributes - loose coupling, encapsulation, cohesive interfaces etc.
Whether the design is 'excellent' is entirely context dependent. Does it allow changes to be made easily? Does the implementation reflecting the design assist the addition of features, support maintenance efforts and lend itself to comprehensibility amongst your team? The team may be more junior and have no knowledge of design patterns and other such practises or the design chosen may be a good fit for your domain.