I'd like to think there are still some Galaxy class ships out there performing the original mission that the Enterprise-D and her sisters never really got to carry out during the TNG era.
The Olympia may well have been a Constitution class ship operating on a deep-space mission as late as 2371, so it's possible that otherwise obsolete designs are still of use on the frontier.
It's somewhat counter-intuitive, as you'd think newer designs would be at the forefront of exploration. But logically if a ship is embarking on a five or ten-year mission, it'll be five or ten years out of date by the time it returns home.
The Olympia may well have been a Constitution class ship operating on a deep-space mission as late as 2371, so it's possible that otherwise obsolete designs are still of use on the frontier.
It's somewhat counter-intuitive, as you'd think newer designs would be at the forefront of exploration. But logically if a ship is embarking on a five or ten-year mission, it'll be five or ten years out of date by the time it returns home.