Again, wizards are supposed to be weaker in the beginning. We have not gotten to higher levels. When we get to higher levels you will suddenly find that wizards are the MVPs. Enemy wizards at higher levels need to be hit first and killed BEFORE they get their spells off, and you will need to protect your wizard so YOU can get their spells off.
That is the trick to wizards. As they become higher levels, they become VERY powerful, so you need to learn at lower levels how to manage them right so that you are most effective with them later.
And limits HAVE to be in place at lower levels so that you get used to them for higher levels when they will be even more of a must for gameplay.
That's why Im hammering this point about long rest so much now. If you can long rest indefinitely at higher levels, wizards will make all other classes totally pointless.