Actually I've been thoroughly enjoying the discussion

It does seem as though
@fireproof78's logic aligns broadly with what the current production team were intending – assuming they were intending anything beyond "this'll be cool for the story we want to tell and the ships we want to show, and the fans will figure out the details for themselves" – but it's definitely not the background or scenario I'd have chosen. However, that's what we're seeing on-screen, so that must be what is. Just trying to figure out how we travelled that long road getting from there to here...
And to be perfectly clear this is not the path I would have chosen either. I don't think the fleet needs to be hugely diverse, but I don't think it needs to be restricted either. But, I do believe that we have to work inside the parameters given onscreen based on what we know of the universe and possible outcomes. So, one, I appreciate the conversation, and two, I do think it's something that fans will figure out for themselves because
that's what fans do. How many times I built different little starships, and starfighters and uniforms and designs to accommodate clear needs in a TOS setting never addressed in the show? I've lost count since playing with my Mego figures.
So, more on topic, I agree with
@Dukhat that mass produced warships were logical, and so I had no issue with the fleet at the end of Season 1. I do also think that Starfleet was faced with shortages due to the war, that were still having an impact a decade later, primarily in the personnel department. Losing a starship isn't just losing a resource; it's losing 400+ resources of people who had already been training to serve on a starship, who understood engineering, or operations, command, science, etc. So, you have to take that time to train those people, get them familiar, and able to continue to support the ships you are building and replacing.
Again, this isn't just a ship or materials or even a production problem, but a people problem. So, if people are busy helping rebuild Betazed, Earth, and other areas impacted by the Dominion War those people are not helping staff ships, but helping in other efforts.
It adds up.