It's also the best way to handle it when you have times where you want "anything but this one"
Also just, we are in an information vacuum here. the only things we know about the D7 for certain is that they're better than the D6 and roflstomped all over our old fleet in the Four Year War scenario. that's it.
We can infer that they may have torpedoes and probably better shields in addition to the known warp 8 engine.
we can speculate that based on the performance of the class on screen (and Sayle's GM history) that they are not a tactically insurmountable problem.
we can worry about sore loser Romulans (*coughTalShiarcough cough*) suppling them with fancy toys to get back at us over the humiliating drubbing we gave the other major empire in the region.
We can fear temporal meddling to disrupt the timeline or to "correct" it.
We can imagine that there are potential unknown unknowns that Sayle is keeping in reserve.
but we can't know.
And in the face of the unknown, especially in Star Trek, I prefer being a bit over-prepared than the reverse.
It's Star Trek. There's things out there, and not all of them are friendly.
(and even the friendly ones might not be safe.)