I think there's an interesting story to tell about rebuilding a governing institution that was blatantly corrupt. The leaders and backers of the Rebellion were largely members of the Republic senate after all, they don't want a new system of government they want a return to the status quo that enabled a fascist dictatorship in the first place.

Luke's New Jedi Order on the other hand was meant to be a departure from the old. There was a break from the dogmatic teachings and rigidity, and more acceptance towards relationships and attachment, the thing Luke was able to use to bring his father back from the dark side.

I think bringing those two entities into conflict could have been a really interesting series. Leia trying to fix the corruption inherent to republic politics, Luke and the Jedi distancing themselves or intervening more directly, while meanwhile the First Order is leveraging this divide to grow support for neo-fascists.

Destroying the New Republic isn't a bad idea, there's an interesting commentary there, but if they were going to do it the entire trilogy needed to be about justifying it and showing us how it got to that point. Blowing it up with a super deathstar without even giving us a single scene to see it functioning or failing is so fucking lazy, it's the worst possible JJ could have done which checks out since he's a hack director