I definitely agree that the issue of identification is uniquely challenging when it comes to marbles. However, when it comes to authentication and grading, I think coins are just as complicated and subjective as marbles—if not more so. Before there were third-party grading and authentication companies for coins, dealers and collectors alike would rely entirely on their own subjective opinions for valuing coins. That's fine for those people with decades of experience, but it makes the barrier to entry extremely steep and discourages new collectors from joining the hobby. And even when ID is impossible for certain marbles, grading can often still be determined because it's a condition thing, not a maker or authentication thing.
I really hope someone comes along and established a method of third-party grading, authenticating and identifying (when possible) for marbles. Without it, I think it will be difficult for marble collecting to survive and thrive beyond the next couple generations.