Idea of StableCoin have no real meaning.
StableCoin it should be stable regarding what?
Stable against the dollar? It means that it will be not crypto coin it will be USD wallet.
Stable against the gold or oil? It means that it will be gold futures, not crypto coin.
Stable its economic property of the coin and not a technological feature. Bitcoin can be stable like gold with sufficient prevalence.
You're completely right. I'm not a big fan of stablecoins either because it either relies on trust of a centralized entity, like Tether, while still having to trust that the fiat you're holding won't lose value dramatically, or the trust of a certain decentralized process, like BitUSD.
But it does play a role in some scenarios.
For example, in countries such as India where the government and the central bank has cracked down on bitcoin transactions, they have relied on stablecoins as a proxy in order to trade fiat against crypto. Of course, I would never consider stablecoins as a legitimate decentralized long term storage of wealth, nor am I concerned about bitcoin's fluctuations at the moment. I completely agree with the statement that with enough adoption, bitcoin will see intrinsic stability.