On the other hand, a lot of the expository dialog and some of the smaller lines felt very out of place and forced. Mike from Resolution out of the blue mention's his wife's pecular sticky note habit, which was laboriously set up throughout the movie prior. He then goes on to say something to the main character (who is having brother issues) something like, "Man, you never know what you got until it's gone. Wink.

"
The Resolution scene was cool, but mostly because I'm a massive
Back to the Future Part II fan and I'm a sucker for new angles and shots of scenes we've already seen. (That episode of Deep Space 9 when they went back to TOS really tickled my fancy, too.) Mostly what I liked about it was that they didn't necessarily undo or cheapen the sublime ending of Resolution, but there's a very subtle line indicating maybe, someday, they'll escape. Probably not though.
On the flip side, the actual two main characters in this *do* escape. And that's where I'm split on whether this should be watched (in order) with Resolution. On the one hand, if you see Resolution first, you might be expecting a downer ending like that movie, and be delighted when the two escape. And watched on its own, the ending felt otherwise kinda... cliche. They sure got away from that mean old smoke monster!
On the other hand, Resolution's "big trick" was the unexpected (but well setup) time reversal right at the end, paying off 100 minutes of buildup. If you know that going into
The Endless, then all the time loop stuff at the start is just "We know!" And it isn't as shocking or surprising.
Aside from the end-end, the last act in general felt like a mild let down. The first two acts did a great job seeding creepy moments or concepts (cosmic stuff like double moons and the sun momentarily flashing dark are things I particularly enjoy*.) But then in the third act... not much. I get why they didn't want to show the monster at the end (watch
The Ritual for a bad/typical example of such a thing), but they could have showed
something. I appreciate there being no jump scares, but I was more slightly creeped out than scared at any point. The way all the characters in the final moments talked and walked around like there wasn't imminent danger also somewhat irked me. And what was with that wildcat or whatever? Felt like extra footage they were able to shoot and then just said, "Fuck it, put it in the movie."