There's nothing wrong with the "good for your age" formulation, in my opinion. This week, the world Masters track championships are taking place at the velodrome in Manchester, England. The guys who win the medals in the 60+ age group would be utterly crushed were they to compete against the Olympic champions. They are terrific cyclists, but in the final analysis they are only "good for their age".
None of us can be as good as we could have been had we trained properly thirty years ago. But so what? We can still be the best that we can be.