Passing through waivers means nothing. They never have a career in no small part because they are not allowed to have one.
The Flyers are not going to learn anything about how effective their scouting, drafting, and development are if they refuse to let anyone play on the margins. If they ever want to compete, they're going to need to change that.
Every other team has prospects that they're able to plug in on the 4th line if they want to. If they Flyers don't, then they've failed disastrously at scouting, drafting, and development for a long time.