Here's what I don't understand - why is anyone wasting this amount of time farming primals for their weapons when they could have easily finished their relic weapon which is better than anything any of the primals drop in the same amount of time?

Now with that out of the way, I don't think there's a single person on the other side of the argument you're bringing forward. SE absolutely needs to add another way to farm Myth tokens, and I strongly suspect that will be in the form of Crystal Tower in 2.1 given its proposed level of difficulty.