All other job quests will have you unlock skills that will change up your playstyle in some way.

For example, Black Mage gets Flare and the barriers, which can open up interesting strategies of popping a barrier instead of moving out of an AOE.

Ninja with Mundras, which allows the Ninja to do some crazy stuff.

Now look at Summoner. You can play the entire game with the emerald carbuncle and once you swap to Garuda, literally nothing about your playstyle or rotation changes. All you got was a remodeled Carbuncle with 10 extra potency.

Summoner has zero sense of satisfaction about its job. A question to you Black Mages, how does it feel to cast a triple flare? Fells awesome right? Ninjas, doesnt it feel great to weave Mundras together for big damage? Summoner lacks that "feel good" to them. Yeah we have enkindle, but its nothing like casting Flare (its also on a 5 minute cooldown) Everything about Summoner is so painfully mundane. Sure we get Fester, but its still very uninteresting. You simply press a new button once every few seconds and after that its back to the boring old rotation.