Angel did love him, but Connor had been too brainwashed to believe him or trust him. That's why Darla had a better chance imo & was able to get through to him for a little while imo. I think Evil!Cordy's hold over Connor was stronger than just an attraction to her, even before she came along he'd been manipulated & brainwashed by Holtz, so that made it easier for Evil!Cordy to do the same thing.

I think that Inside Out does show us that in some way, Darla is still alive & watching over Connor, so I like to think that continued on after that ep too & maybe if the series had lasted longer she would have got another chance to talk to him