It's the epitome of RPG strategy. You can no longer have a 10 mile radius spell detecting all enemies in the area (with a duration that allows your magicka to completely recover before it runs out), and instead have to be more conservative with its use... you have to be more careful and consider if it's safe to expend the magicka that you may need if you run into something. In previous games, you could just cast a powerful, long-duration spell, take some magicka potions to refill your magicka, then head out with full health/magicka/stamina with the spell still active. All the benefits of using a powerful spell without the drawback of drained magicka. With the charging method, you now have to weigh the advantage of a stronger spell, with the cost of more drained magicka.
It's not much different than using weak attacks for limited stamina drain, compared to power attacks with more stamina drain. Or jogging with no stamina drain,compared sprinting with stamina drain. Stronger effect for more cost, so you have to be careful and consider if the added cost isn't going to put you in a worse position than a weaker effect.
Is all flash and no substance.
Its removing the magic from magicka.
Spellmaking being gone is already horrible beyond belief, I simply cannot fathom why such a core feature needs to be removed, but now all thought and planning is removed as well.
Only usuable and useful in the heat of battle, looking pretty but with no content.
No different from psi powers or mutant powers or any other thing like that a million other games already have.