What was wrong with Ultron? I enjoyed his character. But I think Joker from DCEU could have had more screentime. I didn't have a problem with him actually loving Harley since Joker has loved Harley many times before (Lego games and movies, Batman vs TMNT, Emperor Joker, Batman the Brave and the Bold, The Batman 2004 etc.). Just thought his character could have been better explored.

Snoke’s backstory can steel be used in a good way, just have to develop it more

We should have seen more of Captain Phasma

She did had potential. Maybe they’ll explore her character more in future comics

Sir Miles Axlerod: he created alternative fuel just to make it seems low quality and danger. Why? this is useless spending of money. Patent alternative fuel would be more profitable and legal. How to justify it: well, if someone would already patent alternative fuel or if Axlerod wouldn't be the creator of this fuel or even business rival of creator, Axlerod would looking more smart. In first way he may to look (probably) more sympathetic.