Mythics lost the point of what they were introduced to do.
Relics require not only a lot of time, but a lot of money. The people who needed the currency, would sponsor the twice-a-week Dynmis runs, and get to keep the currency. Even then you'd only get maybe 300-400 pieces, and you needed about 18,000 pieces total to finish it. It wasn't just a time sink, it was a money sink. During the first 7 or so years of FFXI, most servers only saw a few dozen players each actually finish.
Mythics were supposed to have been a bigger time sink, requiring more quests, but not a money sink. Unfortunately they included one stage where you need to collect 30,000 pieces of a special currency, nearly twice what you needed for a relic. They made the item very rare, and even if you finished that, you had to do months of repetitive quests in other areas.
With the new Dynamis system in FFXI, two people can duo dynamis for currency, and net them both a relic in a few months. You see them everywhere. No changes have been made to mythics. Even worse for mages becasue all the mage jobs have worthless relics, and amazing mythics, where all the other jobs get a awesome weapon either way.