And yet they still stop that anyways, with Luke inspiring the galaxy, with the FO not doing so well and being in need of becoming a new Empire, and with the galaxy working together and defeating them in TROS.
Well, they stopped the First Order (just barely) from annihilating the Resistance entirely. But that doesn’t account for the rest of the Galaxy that’s being conquered by the First Order offscreen. The First Order wasn’t ignoring everything else just to focus on the Resistance alone. By the end of TLJ, the Resistance barely even exists anymore, and the First Order, despite its losses from the Holdo maneuver, essentially holds the Galaxy unopposed (which is part of why the ending of TLJ is so tone-deaf). TRoS then nerfs the First Order in order to make Palpatine’s fleet matter.