Since the Speed Force can do pretty much anything, can it please stop having Barry holding the idiot ball constantly in season 4? The guy is supposed to be a genius and a really talented forensic scientist, and yet he constantly makes the most stupid mistakes. It's like the writers realised that his powers make him stupidly powerful, but instead of writing creative ways around those powers, they just make him forget that he can use them.
A really interesting thread they could have gone with, after some scenes in season 1 that showed how his perceptions of time were changing, would have been that his powers make him constantly live in that accelerated state, where everyone else was almost standing still, and he had to spend almost all of his focus on just slowing himself down enough that he could actually interact with the rest of the world. It would've been an interesting twist on his powers, and it would explain away why he's slow on the uptake sometime, since he would be so busy just slowing himself down that he'd miss the smaller details. Plus, when he finally lets go and stops holding himself back it could've resulted in some incredible action scenes.
And finally, Barry and Iris together really doesn't work. They have pretty much zero chemistry with each other. Iris felt a lot more genuine in her interactions with Eddie than Barry, and Barry fit pretty well with Patty (disregarding her tendency to shoot first, ask questions never). He's even got more genuine chemistry with Oliver and Cisco than with Iris. So basing the entire plot of season 3 on their relationship just felt flat from the start.
