The original ticket system as was used and intended, 100%.
The original system used demand/capacity/quality to determine the ticket. The weight of each metric varied drastically, so overall, it could seem arbitrary.
That said, the ticket system people use today is more a set of tiers that reflects quality and scope. That new ticket system is very valid, but also somewhat arbitrary. The old system wasn’t arbitrary because if Disney made a ride a C-ticket, that’s just what it was, but the system for determining which ticket the ride belongs to was pretty arbitrary.
The current ticket system still exists both internally and externally, but absolutely is arbitrary, basically just what certain attractions “feel” like to people. It’s not an exact science (internal and external notions could validly disagree), but I’d say generally one person wouldn’t consider a ride an E-ticket and another person consider the same ride a C-ticket, so I think our general system works pretty well.