Yeah, I had a few of the same thoughts on the quick trip to Seattle, but I get it, it's not important and there really aren't a lot of hazards between Jackson and Seattle. Same with the 2 minute scene of Ellie boxing, we don't need a Rocky montage. The first episode showed how little Ellie/Dina cares about the zombies, they consider hunting them a sport because they are bored in Jackson Hole. I would imagine they understand that they are playing a different game now, and not taking unnecessary risks or wasting ammo, time and resources. The Northwest is cold, sparsely populated (if at all), and these two presumably know how to avoid the infected and are smart enough to not walk into human traps, so I guess nothing happened for 800 miles. *shrug* That's believable, it's not like this show is based on Red Dead Redemption 2.
It appears that the WLF have taken over Seattle and defeated or maybe replaced the Fedra there, taken their armaments, vehicles, and fortifications. They will be a considerable force to be reckoned with, especially if Abby and friends are inside the fort or a part of those patrols. I'm not sure Ellie and Dina are going to have a good time if they are going to have to stealthily avoid the WLF army. Those rando Joker-faced people in the forest seemed like a rather capable tribe of wilderness folk that were likely hunted down by the WLF and murdered. They seem to be a lot better at hiding in the woods than Ellie and Dina with a horse will be. That may be intentional on the writers part to illustrate the WLF's tracking capability, it's hard to think of any way this doesn't end up with one of them captured.
We have 4 more episodes to finish this season, so roughly 4 hours of screentime to finish this revenge story line. That sounds about right for them to learn the patrol patterns, scope out the base, set some trap or ambush, fail miserably, regroup, plan a new trap that works, things happen, zombie attacks, then capture Abby and kill her with a golf club before riding off into the sunset. Seems reasonable.