I'll clarify further and keep it rather simple.
Since NIN wasn't designed to be a tank. There was a long and stale period of time for NIN. At first many players adapted with what they had available to get by. Using Evasion setups, Elemental Wheel spam in the mid-lvls and endgame consisted of some NIN/BLM for more enmity generation as it lacked. New abilities and gear tailored for the new role took years.
It was also the devs fault. They basically gave up and didn't define the original role enough and also readjust it if they accepted the community change in a timely manner. Then you have the years of imbalance just between 2 jobs in one tank role. This is what I meant by never wanting to see this again, especially in XIV.