You would think those two paragraphs contradict each other - that as a 4+WAR player Segura could help just about any contender, including as a DH, and be worth the salary. But the way teams manage their rosters and payrolls is more complicated than that. I agree, there's probably not much demand for him and the Phillies need him right now more than they need whatever his trade value is. If you could actually get a package built around a Top 10 prospect for him, different story perhaps.
As much as I appreciate CD's point that a team like the Rays would get ahead of this, a team like the Rays wouldn't have had $30 million committed to a player like Segura in the first place. And even if he was cheaper but had his big salary bump coming, they'd do that deal in the off-season, not while they were in contention mid-season.
Of course the Rays would also trade Wheeler this coming off-season (again, if he was a controllable player, they don't sign players like Wheeler to big contracts in the first place).