The belt system isn't the problem, the problem is that you can win a world championship at each belt level.
Years of experience is better, even if it's hard to prove and that 5 years at 5 times a week and 5 years at 3 times a week or with a 5 months off because of an injury. In my area there are no gi competition that are based on that data (up to 1 year is beginner, 1-3 years is intermediate, after 3 years it's the expert division). Then the beginners would be able to compete among themselves.
It's hard to care in the system we are in. If you win, you ask yourself if your coach let's you sandbag, and if you lose there's likely guys that are sandbagging.
Belts are for your coach, it helps him to show you your progress. I understand what a purple should look like in my gym and I work to get to that standard, I don't really care about what's going on in other gyms.
For the black belt, it's more of an aknowledgement of your knowledge and skills, it's a way to say, you're now ready to be a coach and I assess that you're now an expert. There are no belts in wrestling, boxing, kickboxing, MT, MMA... But most of the coaches have been aknowledge by someone to assess that they are legit experts.