For one, it’s a major way the film apes ANH, but on a more ridiculous scale.
Second, it has no emotional impact. Just adding in the deleted scene of Leia’s messenger being sent there doesn’t do enough to give the audience an emotional anchor. And again, it has no bearing on the later films. The only reference to the NR destruction in TLJ is the crawl and a Hux line toward the beginning. With the NR still intact throughout 8 & 9, the lack of response from allies can be recontexualised by either editing or the viewer as the NR continuing to not help. And the arrival of the fleet over Exogol in RoS could be contextualized as the NR finally sending aid.
And finally, I think the destruction of the NR was a very shallow way that the writers were signaling that they weren’t going to be beholden to Legends material, since the NR plays a not insignificant role in Legends. They then of course still borrowed the concepts of Jacen Solo, a hidden fleet, force clones, and Palpatine’s return… I just really feel like it’s useless and goes nowhere.
Personally I think removing the Super Weapon concept at all, if possible, is ideal. Starkiller would just be a FO base that they assault to rescue Rey and because they might have a chance at killing Ren and Hux. Idk…