It's best to pretend this movie didn't happen as even the movie itself does so through it's ending. I could go on and on about how the characters themselves poke fun towards the bad writing. Action was pretty good but the story wasn't. Spoilers:
Many characters die throughout the movie. But there's basically little to no reaction or effect on the overall movie. Strickler, who is literally now Jim's stepfather, dies for nothing and then is just forgotten about. But of course this was so we could have more important scenes such as Steve being pregnant. And the ending, the ending was just something else. Generally I'm not a fan of time resets unless they are very well executed and have a very logical reasoning to it. Here it's just "oh no our friends died and we really care about it now despite having only small reactions in the moment, guess we gotta reset all of time back to zero." This feels more like a last resort in a situation which feels like it's not needed. If we had seen entire cities leveled or at the very least characters reacting to other characters deaths beyond just "oh no anyways" then maybe it would feel justified.
Regardless of whether it's justified this does mean every interaction, bond and achievement the characters made on their journey are gone. Which is obviously a big kick in the face. A bigger kick in the face is toby being the new troll hunter. Now here's the thing, it's been established throughout the series that Jim was *chosen* to be the troll hunter. It wasn't just a first come, first serve thing. Toby was even there when Jim found it originally but for some reason it just went to him now. This is strongly implied to be because he said all those quotes before dying that were about being a troll hunter. Except that was the toby that died. The toby that went through multiple seasons of character development and still wouldn't really be the guy I'd trust with the troll hunter amulet. This also goes against the reasoning behind the time reset as it was for Jim, the one who knows what will happen, to save everyone as the troll hunter because he can accurately predict the cause of their death. So why on earth, even if it was actually possible, would Jim give it to Toby. A clumsy, overconfident kid who does not know what's going to happen and was indirectly responsible for the titans being summoned due to him breaking the train brakes and ruining the plan to defeat the arcane order. There is no reason for this, they just wanted to sound deep for the finale.
In conclusion the only good decision this movie made was that it never happened.