There's another point that at, 32, Dubravka is still a developing keeper as well but a stone's throw from what should be his prime. He had a brilliant start to life in the Premier League and you'd expect him to keep going from strength to strength. But his progress has been halted because a different keeper with a lower ceiling has been performing to a standard which makes him hard to drop. It's all just another example of poor squad management. It's rife at Bruce's Newcastle.
Edit: I will admit to not having done any research and therefore may be relying on clichés when it comes to goalie peaks being much later than outfielders. But considering things on a case by case basis, Dubravka was a relative unknown and a bit of a late bloomer in terms of playing at the top level. Not exactly Jamie Vardy but the highest club level he'd played at prior to here was probably Allsvenskan. He knows the Premier League better than he did two/three years ago so you could reasonably expect him to be coming into his best years now.