I guess yes, but if cryptocurrency is dominated by stable coins then this industry will get boring. And many investors will turn its back unless this stablecoins are like security tokens where holders can get a share of the company's profit.
I agree with you, if the coin is stable, it will be difficult for investors to profit, it is precisely where the uniqueness of the altcoin cannot be stable, it can change at any time in unexpected periods of time.
There is notting much any one can do about the stability of bitcoin and altcoins price except the forces of demand and supply. It is the laws of economic that bitcoin is also following. If the demand keeps increasing which will likely happen then the volatility will be there no matter how many stable coins we have in the market.