If you look into it the lore of TFA isn’t all that confusing, there’s the New Republic which is dealing with Imperial Renamnt terrorists, the First Order, who even have their own ripoffs of Palpatine and Vader (one might ponder if their appearance is intentionally similar, to get more people remembering the OT). Leia wants to fight the First Order while the New Republic would prefer to let them be.
The problem is all in the presentation. In the thrill of the action, you don’t think like above. But they could have easily fixed this. Go to the Republic’s capital and listen in on a Senate meeting (like TPM). And properly build up Starkiller (like they did in Ep4 and 6 with the title crawls) instead of just showing up halfway through the movie and taking all the spotlight.