It's really, absolutely, not convoluted at all. They picked up a story beat that was never explained by Epic in the old trilogy and made it work by adding a couple of small details. I know you have a tendency to drift off and start thinking about breeding the perfect Pikachu while playing other games, so just watch the cutscene again on youtube. The only weird thing about it is that they kind of expect you to have played Gears 2 & 3 which I think is weird for a shooter to ask from its audience. But as someone who did play them, I'm really happy that this entire thing has some continuity now. When Gears 4 came out it was hard to make out whether they wanted to move forward or expand on what was there already – Gears 5 kind of shows that they want to do both, but needed a second game to really find their rhythm.
The boss fight in Akt 2 was pretty awful though, I agree. Took way too long to finish because it seems like it was designed with coop-play in mind (he always freezes with his back turned away from you so you waste precious time circling him and Del doesn't really shoot him most of the time).