I'm so confused. Fireball? That's a damage spell. If you want damage, why on earth are you playing a wizard? Wizards are for control.
In the language of the formal 'Controller' Role, Fireball, and other AE spells, are 'control' because they annihilate large numbers of lesser enemies. Thus, 'controlling' them via that most primal of lock-downs - death. Kinda like "pest control."
The threat of AEs like fireball - and ongoing AEs like a Wall of Fire - also exerts 'soft control' in that it encourages enemies to avoid an area of the battlefield or to keep spread out, limiting their movement/positioning choices.
That's only one way to play a wizard. Wizards were exclusively about control in 4e, but not so much either prior or before.
The 'Controller Role' was funny in 4e. It wasn't as clearly defined as the other three formal Roles and wasn't supported by one or two obvious class features. Leaders got a class feature that triggered an ally's surge. Defenders got class features that marked. Strikers got class features that increased damage directly or indirectly. Controllers got, well,
better powers than everyone else.
Ostensibly Controller party contributions included minion-sweeping, area interdiction, soft-control/debuffs, hard-control/lockdowns, and even more nebulous things like 'changing the assumptions of the challenge.' But the bottom line was more, more varied, and more potent powers than the classes of other roles - and for some, more flexibility/choice built into those powers, as well, particularly the Druid, which swapped available powers round to round based on whether it was in humanoid or beast form, and the Wizard, who could swap out daily and utility powers (and, in Essentials, encounter powers - /and/ was the only class who could re-train powers without losing access to them). They also tended to be Ritual Casters, adding to their breadth of non-combat options.
Wizards, specifically, were secondary strikers, perhaps, more accurately 'blasters,' since they could be customized to do striker-like damage, but to multiple targets, overlapping the Sorcerer a bit (though not to any where near the point of strict superiority claimed by critics of 3.5 & 5e), but that was nothing new and is still the case. While wizards could do some buffing/de-buffing they didn't much step on the toes of Leaders - which has always been and remains the case, healing is verboten to the Wizard for whatever reason (of course, healing is also arguably a 'burden'). Similarly, Staff builds and the Bladesinger sub-class could be tough enough to operate in melee, but not to the point of being secondary defenders, also nothing new (Bladesinger dates to 2e, 3e wizards maxxing concentration could be functional melee) and still the case (5e wizards can be pretty tough, especially the oddball heavy-armor wearing dwarven builds and Abjurers, and SCAG re-re-introduced the melee-capable Bladesinger).