He's a useful player, just not a cost-effective one. WAR valuations aren't what matter here, compared to the unbalanced Phillies payroll and MLB's changing market conditions.
Plus a not insignificant part of his value to the Mariners - and the Phillies when they traded for him - was his ability to play SS. Now the three best free agent SSs on the open market all signed for less, and you can get a 2B (like Wong) for almost half.
Obviously it will be great if he can still hit that WAR target going into next season, whether because he sticks around or because it means he could still get traded. And if not, one dead year from a big contract on an older player is hardly surprising, though in Segura's case we also gave something up for him, unlike Ibanez, Polanco or Cutch (or Lee the second time). None of it has anything to do with him really, it's just money that could be better spent elsewhere