The Flyers are rebuildling, rebuilding in the NHL with the salary cap is similar to baseball, in that you draft kids at 18 and for the most part it takes 4-5 years to them to become NHL starters (the exception are top 20 picks who often get to that point in 2-3 years, but even then it varies).
Hextall started in 2014 after Holmgren treaded water for two years (sound awfully like the Phillies under RA!), so he's only had four drafts - yet they already have Ghost & Laughton (holdovers), Provorov, Konecny, Patrick, Lindblom and Sanheim up. And Couts as a major star (all of 25). Next year they'll bring up Morin and NAK, maybe Frost makes the team, Vorobyev and Myers at some point, and for depth, Knight, Vecchione and Bardreau. In 2019, all the guys who'll be in LHV next year will be pushing to make the team along with Ratcliffe.
Up to now, Hextall has loaded this team with a lot of mediocre veterans that didn't cost any assets, Mrazek is the only player he's traded for and given up a draft pick. Ron and Hakstol played the veterans because some of kids weren't ready to carry a heavy load, no different that baseball when you shelter a young pitcher. Sanheim got easy minutes and still struggled, he has great skills but not great instincts and needs to hit the weight room. No every young player is a Provorov. Hextall is conservative when it comes to player development, he's rather lose a season bringing a player along slowly and increasing their odds of success.
The next couple years they're going to have a flood of prospects pushing for jobs, and at some point Hextall is going to have to make a quantity for quality trade, but it'll probably wait until the goaltending situation is resolved, i.e. Hart is ready to start - he's been absolutely dominating in juniors this year and will start in the AHL next year.