Wasn't voyager CGI at this point? Before they had to use models and kit bashing, but I remember they made a big deal that Voyager was all CGI. If it was CGI then it was a definitive choice to include the Excelsior, and not just a reuse of a model.
I really don't have issue with it still in service. All the tech manuals state the ships were able to upgrade easily. Doesn't the Galaxy have a bridge that can be swapped out easily as it is a module? Which explains the differences in the TNG enterprise bridge versus the Generations enterprise bridge.
I would expect they'd still need something to base any CGI model on, and it would still be easier to take an existing ship then to create a new one. Also, it may not just be about re-using anything - but also to showing the audience something familiar. I suppose we can be lucky they didn't put a Constitution Refit in anywhere. (That may be for the same reason DS9 and VOY never had the Sovereign - it's the movie "hero" ship and they want to keep it "special")