Lazarus
Fleet Captain
It wasn't really laziness in TNG or the early years of DS9 and Voyager. Back then they were using physical models, and those things cost a lot of money to build.
Why are people calling it 'laziness'? It isn't lazy to reuse model shots since creating all-new studio models that stand up to filming is very time-consuming and expensive. How many times was that Talarian ship used throughout TNG?
Yes that SAME SHOT of the excelsior-class pulling away from the Enterprise-D was used too much, but to expect new types of ships every few episodes, particularly during the days when shooting-models had to be built, is unrealistic.
To be completely honest it actually makes MORE SENSE for episodes to contain the same types of ships on a regular basis. Starfleet has too many ship-classes as it is, dozens upon dozens of different designs for vessels that do more or less the same thing.
Personally I can't see why there would be more than a handful of different Starfleet ship types, mass-produced spacecraft that have been tried and tested over many years.
Also these Starfleet ships should in theory have a minimum life-expectancy of a hundred years with a few major refits in between. It makes sense that the 2360s are full of 60, 50 and 40 year old excelsior class ships.