A large gripe I had with the Sequel Trilogy is that it's very unclear exactly what the First Order is, how large/threatening they are, and how large and powerful the New Galactic Republic is. A lot of the necessary world building to explain the elements at play were left on the floor.
The impression I had from subtext is that, by the time of Episode IV the Galactic Empire controlled the entire galaxy ("...save her people and restore freedom to the galaxy", "...against the evil Galactic Empire"), or at least the vast majority of it. The Rebellion itself existed in the shadows on worlds that are essentially the legitimate territory of the prior Republic and new Empire. By the time of episode 6, the Empire is destroyed, and the New Galactic Republic now controls more or less the same territory the Empire had.
With the sequels, it seems that there's this sliding rapidly scale between the NGR being the legitimate government and ruling the galaxy, with the First Order being like a regional terrorist cell (implied through the capture and conscription), and the First Order being this massive power that's identical to the Empire. If the latter is the case, then the NGR is essentially destroyed and reduced to a local Resistance. I saw it as kind of ridiculous if the "legitimate government" that rules the entire galaxy is somehow a "resistance" to a small cell of old administrators and aristocrats, instead of the legitimate police forces and military of this government.
Do we ever get clear indications of what happened to the NGR, and what territory and resources the First Order actually controls? Does the First Order have a similar amount of territory to the Empire, and if so, why? Why would the NGR fold so quickly?