You're both correct. Some of those guys could be stars but aren't yet. But the the guys the Astros ands Cubs had were farther along at the time they started winning. Hoskins might be a star but he's not as valuable as offensive stud who also plays a premium defensive position. Herrera and Hernandez are great but not at that Correa/Altuve level.
If the Phillies were truly interested in Cashner, Garcia or Vargas and they all go away, perhaps that will force their hand. Or maybe they've been more interested in the higher-end guys all along.
I would trade for Stroman in a heartbeat. The Phillies have talent and depth to trade with. They'll have even more next year (unless all these players stink, in which case they have bigger problems). To get a 26 year-old instead of a 31 year-old has significant, significant value, and that's even before you factor in extending him. When you look at the trades that have happened in the past year-plus - the Cubs for Quintana, Yankees for Gray, Astros for Verlander, Gerrit Cole - those are all deals the Phillies could easily make. When they're ready. They certainly will be next year, at which point they will ideally have a lot more redundancies if Franco, Kingery, and Williams/Altherr/Quinn all perform (which won't happen. But hopefully most of them do).