How would you have felt, had that actually been "our" Enterprise-D, rather than it going down the way it did in Generations? (Of course, we'll have to assume it happened slightly later, short after the conclusion of TNG in that case). Perhaps with a line that explained that fortunately, most of the crew got into the escape pods and through the wormhole in time, or some such thing, to explain how they could reappear in the next movie?
I don't know how these things work exactly in the writer's guild, but in my line of work there's this small thing called "job satisfaction". (And to me, one of the key ingredients in sufficient job satisfaction is that within a clearly established goal, my employer gives me enough freedom to do what I think is best , and then use that freedom in order to create the best possible product for my employer within the time and resources allotted, one which I am convinced is high quality myself).
Low job satisfaction usually results in a high employer turnover rate, which isn't good for the company, especially not if it concerns positions that aren't that easy to fill (which I would assume would be true for experienced writers for TV shows).
And even if you find decent substitutions, they'd probably still have different ideas of where to take the show next, not quite meshing with how the show originally was set up, which in turn probably isn't good for the continuity of the show, even if the refreshment itself was needed, etc.
