i don't know how much of it is casting, per se... i think anyone of the dc characters could be synonymous with their actor (aquaman is a big one here) but the direction is so... awful. i said it when BvS came out but batfleck is a PERFECT thomas wayne batman. absolutely perfect. unfortunately bruce wayne and thomas wayne are two very different batmans. i think gal gadot does pretty well in the action sequences... she has a great game face, like she's EXCITED to beat on some giant monsters. which fits wonder woman perfect. but outside of fight sequences she just... is kinda there. henry cavil LOOKS like superman. he's got a great physique and chiseled jaw. but the CHARACTER behind him is... just... empty...
with marvel, even the silly easter eggs with captain america making public service announcements for school... you can tell he BELIEVES everything he's saying. i'm not saying chris evans is a better actor than anyone in the DCEU, but his character is just so much more believable because his motives are internally congruent. sure, the DCEU might LOOK better in certain aspects because they are leaning so heavily on the nolanverse ambiance... avengers is all bright and vibrant colors but the end of the movie shows civilians bloody, broken... yeah, the avengers saved the day but at what cost? that has been one of the main themes of the MCU and it makes a huge difference.
and that's the crux of the matter... all the DCEU characters are vapid.
cap stands up and says that you fight the good fight not because you can win, but because it's the right thing to do. thor comes around and says that you fight monsters and villians not for personal glory, but because if you don't, those monsters will kill innocents. he fights for the 9 realms for PEACE. even ant-man says you fight to be better than what others say you are. i mean, these are all pretty lofty ideals. the justice league on the other hand? i only watched it once but i couldn't get behind any of the characters.