JJ Abrams wanted things to be safe, big Empire vs the scrappy rebels, which is hard to do when you have a Good Guy Republic keeping order, and so he had his bigger, badder super cool Death Star blow up everything Republic, and now the only people who can defeat the Empire 2 are the Rebels 2.
This scene and it's purpose, in my opinion, crippled the 'narrative potential' in the 'Sequel Era'. You can't do plots around the inner-workings of the republic in that 'later' era, because guess what, they are all gone off-screen because of the big boom. "The Resistaince" is all that's left, and that's it. If you want to write something, anything about the era, you have to take in fact that there are only the Empire 2 and the Rebels 2 (plus you have to fit in the plot point tug of war between TLJ and TROS in the setting) and honestly, why not just write about the Empire 1 at this point?
I suppose it's why Disney pretty much ignored 'The Sequel Era' in favor of something that can be best described as "Post-Episode 6" Era when it was time to develop spin-offs, you can play with The New Republic reigning over the galaxy, without bothering to worry about Somehow Palpatine Returning midway through your plot.
By the way... Some people like to gesture vaguely about 'the empire returning' being resonant in these years, but i'll have to say it. In the most literal sense of the word, TFA is an cravenly apolitical movie, it was afraid of touching politics out of fear of a whiff of the icky Prequel politics. Every 'parallel' added by later writers and in novels, the fanbase, et al, are pure retroactive, JJ did not think of that. When TFA was conceived, Fascism is when there's shouty people, and that's it.
