Why the Secret Spell Scroll system would have never worked.

But it doesn't CREATE any mesos. The problem is the excessive amounts of mesos flooding the economy. There is too much mesos, and mts is not where it came from. mts assists the process and provides motivation, sure, although it isn't the root of the problem. Once the duping stops, mts will stop being a problem. Even without mts, duping would still be a problem. Unless they stop the duping, MS is totally screwed quite frankly.

Also, from my understanding the SSS actually evade trade tax.

Duping SSS creates meso, botters create mesos. But all is pointless if these mesos can't be turned into NX. The MTS creates an easy path for those that create mesos and inflate the economy to profit of it.