The Russians are catching up in terms of fuel efficiency, even in maintenance. They are not as good as PW, RR and GE, but they compensate for the difference with significantly cheaper costs.
At 2.3B rubles, the Superjet costs just $24M. An equivalent A220 costs $80M. So in the 100-seat segment the Superjet is unbeatable. If they make a 150-seat jet for $35M or so against the A320's $130M, then they will start dominating the market completely. Tata and Indigo recently ordered 1000 such jets, their next order could be for 2000, and most of that could go to the next Superjet. No one's gonna care about engine efficiency when the procurement cost is 4 times lesser.