Be good exchange for trading maybe yes, but be the best is something that can't be decided by someone. But maybe if want to review and give good opinion, i think it is ok. But for me any exchange is good because we can use all of it.
I won't recommend kucoin as the best exchanger so far because Binance has been there before kucoin if am not mistaking and as well as BITTREX. What we should even look out for in exchangers of now are: maximum security of funds and a 24/7 customer service to attend to the community.
KuCoin is still too young. For the short period of its existence, the exchange managed to attract over 2 millions of traders, and this is a real record. It attracts clients with different promotions and tokens that are shared among its customers. It is not the number one exchange, but I guess, we can use it if good rates are offered at KuCoin, and it is very safe.