Demand for Russian built airlines
in Russia /= them being competitive with Boeing and Airbus. The USSR built airliners as a strategic priority for the domestic market for decades: their track record of being terrible was one of the reasons behind scepticism of the Superjet
And airlines in most countries have far more to worry about buying aircraft whose maintenance depends on a faraway pariah state and that are not certified in Europe than they do about US sanctions targeting them. And even if they do, still not necessarily more difficult to circumvent the sanctions (as Mahan Air did with wet leased 747s) and access a worldwide parts supply and MRO market than rely on being able to maintain and sell on your Russian aircraft at reasonable price and timeliness...
It would also be surprising if the new Russian engines were competitive on performance with new Western engines, and likewise with other components they've had to switch to domestic manufacture for.