I think that was
@Steampunkette 's point. It isn't hard to balance, but hard to do in a satisfactory way that would still feel like D&D.
I'm with you, I like different roles where each have strengths and weaknesses, so that the party has to work together to accomplish their goals. So that if one member goes down, the other feel that loss.
The problem that I have with Wizards in 5e, is even at lower levels, they start feeling like they are stealing the spotlight from other classes.
I'm feeling this about D&D more than ever now that I'm running Warhammer Fantasy 4e. In Warhammer, Wizards can have various utility spells that step on the turf of other careers. They have cast incredibly powerful spells that will devestate an enemy, but there is real risk in casting magic and real costs to mitigate those risks. This has the laudatory effect of being cautious with magic. Why take any risk to bypass a locked door when you have someone who can pick it? The miscast and chaos rules in Warhammer mitigate the "magic can solve anything" issue far better than spell-slot resource management.
Inject some risk, through possible miscasts, casting times, etc. The more powerful the magic the steeper the cost. Keep cantrips so their are some safe attacks the power up as wizards level up so they can always contribute, but make levels spells have some risk in the casting.