Most Scottish clubs are fairly decent at giving young players a chance (maybe with some exceptions). The problem is the players being produced by the youth system clearly aren't good enough, so the problem probably starts even younger. Probably the coaching, idk.
If all Scottish premierships played Scottish centre forwards from the youth team who clearly weren't good enough that wouldn't make things any better for the national team. Blaming foreign players is the easy option when the issue probably starts with the quality of coaching.