Given that fortify destruction only reduce magicka cost, is there a way to hit harder?

TLDR: Destruction magic sucks.... especially compared to bows.

So, to improve the damage of destruction magic, there are 6 ways to do this. Reference the Perk Tree for the first two.

1. Pick the branch of the perk tree for your favorite damage type... preferably all of them (see below) and pick up the appropriate damage increase (e.g. Fire magic, augmented flames) and max it out.

2. Pick dual casting from the right side of the perk tree, then pick Impact (doesn't improve damage at all, but fairly important to be effective.)

3. For any particular opponent, pick the appropriate type of attack (e.g. don't pick frost for Nords who are resistant to cold, do pick fire for Trolls who are vulnerable to it.)

4. Max out Alchemy and brew potions of Destruction.

5. Brew potions of Weakness to X (Fire/Frost/Shock).

6. Get the most powerful spells of the destruction class (e.g. Incinerate or Firestorm for Fire).

And then, in combat, identify the appropriate type for your opponent, shoot an arrow poisoned with weakness to that type, drink a potion of Fortify Destruction, and then hit the opponent with the most powerful spell.

And, from all that, you can now see why it sucks. Because you can improve archery base damage with multiple enchanted items (necklace, ring, gloves, headgear), with multiple archery perks, potions of fortify archery, AND improve the bow with smithing, AND double enchant the bow, AND buy the best arrows, AND Sneak attack (doesn't work with destruction) AND poison the arrow.

So, in DND terms, the action economy for archery is 1 shot 1 kill, but for destruction, it requires 2 actions, one to poison the target and one to hit it with a spell, PLUS it requires a nearly encyclopedic knowledge of opponents elemental strengths and weaknesses.

Mixxiphoid has made some suggestions, and I've researched all the links. Note that I've not used these, so you'll have to see if they address the situation (and maybe report back).

The mod Arcanum - A New Age of Magic by noptasis is available on Nexus for Skyrim SSE and is also available on Bethesda Net uploaded by KosorsomesayKosm for XBox One.

The mod Midas Magic Evolved by darealslenderman is available on Nexus for Oldrim.

Also the mod Apocalypse - Magic of Skyrim by EnaiSiaion is very popular and could address this as well. It is available on Nexus for Oldrim and Skyrim SSE, and also on Bethesda Net uploaded by EnaiSiaion for XBox One and for PC.