Any talk of 'fixing summoner' is going to have a lot of tension between the people who enjoy the current job, which is enjoyable, and the people who don't because it fails to evoke (heh) the very iconic final fantasy job/concept people have a lot of attachment too.

I don't think it is impossible to satisfy both needs, but I think it is important to recognize the second camp is super valid even if they don't play summoner at all right now. It is probably up there with Red Mage in how iconic it is to the game line and the integration of your actual summons into your identity leaves a lot to be desired. And even though Red Mage couldn't actually be a healer/damage hybrid because trinity, they did a good job of heavily integrating its identity as a versatile caster into its kit in a way that satisfies that callback.

But like... the problem is that in most games summons are either 'super spells' or pseudo-limit breaks? Or entirely alter the composition of your party? They are mega-iconic because they mechanically signify something 'bigger' than other mechanics, and that obviously doesn't work in an MMO (at least, without entirely changing summoner to being some absurdly high downtime caster or something, and that already is evoked a bit by how you cycle to getting the 'big' summons, it honestly does feel like your charging up your call meter through the fight, its neat). However, even little touches, like making more of your personal spells summon 'stands' like Dreadwyrm Trance does would do a lot.

Like having every aetherflow ability and major oGCD come with a flashy egi or mini-primal doing a thing for you would be a great way to make your big spells feel like mini summons. Carbuncle could do Fester, Tri-Disaster would be a great way to get our other three ARR primals (No, not you King Mog, maybe you can do addle or something you irritating piece of garbage, we got the tech to make job actions visually different based on how the ranged ones do Peloton) in there. Devotion could have a summon associated with buffing show up above your pet so its not weird that Garuda is giving people damage.

And, of course, Egi glams (and maybe even letting you glam the starting 3 as whatever summon you want) because people identify strongly with summons about as much as they do with pokemon.

Its way less about summoner actually being different and more about it feeling different. Visual feedback is huge in how abilities impact you and how a job feels, which is why despite doing only 150 potency landing a bloodletter feels way more meaty than doing say... a 250 potency cascade on dancer. Its the aethestetic fantasy that is really failing here, not the mechanical one.