If there is always a new coin out then you have no choice but to use trading platfroms even they are not acting as a wallet. No way new coins will be just implemented if there is a standalone wallet that can support multi currencies.
Bit.Ac is a web multi currency although I don't if there service is still trustable. Let's wait for other feedback.
There is no safe wallet as of now and i am always heard about the jaxx issue so if you really want to hold more than 10 altcoin in the same time for safety install wallet separated in your own pc..
Well since yobit is alive for a long time i think you can use their service but saving your altcoin for a long time is not a good idea.