it seems that there will never be a coin that can be stable, everything must have an up and down price movement which will be influenced by a very high demand, so a stable coin will show that the coin has no good development.
of course there is , do you here about usdt ? that is a stable coin and that is under on crypto category . being stable doesnt mean that a coin has no development , sure it is still being develop but its just doesnt have a volatile nature just like what we have on cryptocurrencies such as bitcoin , eth , bch , etc .
speaking of bitcoin , bitcoin is experiencing a stability right now because its value isnt moving for a long time although this might change verry soon .