1. So here is my example. In D&D, you use a spell slot and cast fireball. It does damage in an area guaranteed. Now, how much damage is complicated based on saving throw, resistance/immunity, evasion or other features, legendary resistance, etc. But the effect is consistent. Compare to something like DCC's system where you roll to see how effectively you cast the spell with a poor roll and do barely any effect to roll high and blow up your party. That fits DCC's style which is very yolo, but I don't find it fits D&D.
2. I must preface with the assumption of ceteris paribus. The question was how would you nerf the wizard, not how would you fix other classes to fix the imbalance. I do agree I'd rather buff classes than nerf, but I'm keeping in the spirit of the thread.
3. To me, the fantasy of the class is someone who can use magic as effectively as a fighter swings a sword. I don't want to shoot a crossbow, I want to shoot bolts of fire from my fingers. I want to create magic shields, float above the ground, and use complex magic to overcome obstacles.
4ish. I want to feel competent, not overpowered. Previously, magic users started out incompetent and ended overpowered. I want to adjust the range and scope of spells rather than overhaul the whole of magic, and I'm willing to sacrifice things like wish to keep the wizard's power line in check.