This is no issue at all..Whatever clothes they must have worn in those times, it's not necessary that in serials they must wear the same thing..if they wore unstiched dhotis and saarees, if they show them semi naked then people will say that it's looking vulgar!
costumes must look decent & beautiful ..just to be close to reality they can't show the characters semi naked. Shri Krishna had the most gaudy clothes & garish make up ever used in any mythology..
The palace of Kans and his clothes can be of any color, black or blue or gray or white! how does it matter? it's the imagination of the creator of the serial..
it was told in the serial that all his friends of his age were killed by pootna..most of his friends were actually elder to him...their complexion can't be an issue!
Regarding the story, they have to show the bal leela in detail bec. probably won't show the complete lifetime of Krishna (i'm talking about Mahabharat & after post Mahabharat story)..Perhaps they've planned to continue the serial only till Kans death..and how do you know it's ficticious? have you read Shrimad Bhagvad Puran?
Devki and Vasudev wearing jewellery is not that big an issue ...it's not a flaw....It's not right to analyze a mythology this way..i can point out 1000 flaws like this...u can also say there was no make up at that time then why are the ladies wearing lipsticks and eye liners?
For your information, Jai Shri Krishna is the highest TRP gainer in recent times along with Balika Vadhu. JSK and Balika Vadhu amongst the top 5 serials..no serial got this popular in such a short span of time..showing cutie pies won't make a good show but the packaging of the show is perfect along with casting, costumes, dialogues & music..It's one of the best shows on TV today..
Charu