Summoner doesn't feel like it Summons.

[Atamis]

Summons in FFT did not smash the entire field, they just had a slightly bigger radius then black mage spells at a higher relative MP cost and charge time.

Sylve said FFTA, Tactics advance, where they did indeed smash the entire board. Tactics (Original ps1 title) was different and was just small-medium area.

While I agree Summoner was in essence an advanced black mage, I feel that grossly oversimplified it, as Summoners were also white mages, and general support classes. A few dedicated Summoner characters only had access to white or black as basic spells yes, but the summons themselves generally covered a wide range of stuff from carbuncle shields/reflect, to party wide raises, huge party heals, and all types of elemental attacks.
I think the essence of summoner generally boils down to using spiritual beings to effect the flow of battle. A black mage casting fire 1/2/3 doesn't have the same effect as casting Ifrit even if they essentially do the same fire damage. This of course varies wildly by game.

Its kinda weird to think about, I can't really think of anything that comes close to the final fantasy style of summoner. In other games a summoner is just a generic pet class with generic ghost-pets or minion swarms.