From my understanding its because in ffxi we did everything via our pets, few smns in xi actually did much casting and even fewer pulled out their staff and started clobbering, so the job revolved almost entirely around your pet. There was a massive disappointment with egi but from what I remember back at its reveal was it was because a 12 year old mmo had better summons than this new installment both graphically and functionally, then to add insult to injury egi were mostly left to their own devices. So it really didn't feel like a smn at all because you summoned an egi and forgot about them. They were a glorified auto attack.
imo ffxi did the jobs in the series more justice than any other game in the franchise for the most part. Not only were they able to go dark, real dark in a lot of cases, with the storyline because they were not concerned about making so much of the game cute or whimsical. But some jobs like smn, blu, rdm, these were all dang near perfect versions of them, esp blu and rdm. But that was because the jobs could be so large, expansive and detailed. You had actions for everything because they threw everything at you instead of trying to limit everything for simplicity. Not to mention they had no concerns about speed. You didn't need everything right now, that game is all about the long run.
This version of smn is more of a traditional summoner from a solo ff game. You summon your pet, it appears, does an attack and disappears, leaving you to do your own thing. So they are literally just giving us smn, its games like xi that are the deviation. So I am not too worried, nor am I freaking out about it, esp since we have no real idea how it will play.
Simplification is the #1 rule too ffxiv at this point, so screaming that its not complex enough is silly. You know what you are going to get when you log into ffxiv. You know what you are going to get with job changes. You know what you are going to get with new jobs. If you really want a challenge or complexity in how you play, this is seriously not the game for you at all and I have no idea why ppl still cling to the belief that it is or someday will be.