The problem with the young pitchers was simple, they were pitching longer and under more pressure than they had in their careers, and they're works in progress, look at Eflin throwing changeups his last start, if he could consistently throw a plus changeup he'd throw fewer FBs, less wear on his arm, more weak contact and more IP. And so on. Arrieta wore down and his command deteriorated, Nola is hitting 200 IP this year, far beyond his previous high.
I doubt we have a shot at Machado, and Harper is not a "game changer," he's a slight upgrade in RF.
Any other 26 year old FAs this year?
Patrick Corbin is the only pitcher worthy of a real contract, and he scares me, two mediocre seasons, followed by a big contract year performance, he's a guaranteed disappointment if you''re expecting 5-6 WAR, his two best previous years were around 3 WAR. Durability is also an issue, he's not a workhorse and you have to wonder if he'll hold up. His money pitch is his slider, but he lost velocity on his FB this season. He's also been aided by a good defense.
If you want a read on how good our starting pitchers actually were, check the chart toward the bottom of the article that gives xWAR and see how they rank among all SPs: