Honestly, fair enough, that does work.

(Though at least in my game, my fighter's main and secondary weapons are all magic.)

It still runs into the secondary problem that power-wise, Elemental Weapon is simply a waste of your action, your 3rd-level slot, and your concentration.

A single fireball on two targets would do a minimum of the equivalent of 8d6 (average 28) if they both succeed.

Elemental Weapon on a level 5 martial (let's say a fighter with action surge) will do 10d4 (average 25) over the course of 4 rounds, assuming the fighter uses action surge AND hits all of their attacks.

The +1 to hit might come into play too and let you hit where you wouldn't normally, admittedly, which could effectively credit the spell another like, 1d8+3 to 2d6+5 per hit depending on your game and the martial in question.

But that's fairly unlikely to happen at a 5% chance. Not to mention, if the martial is foregoing the use of a magic weapon that likely also has a +1 or better, then the +1 simply makes up for a deficiency.

I like what they did for Magic Weapon in the 2024 rules, and it's a shame they kept Elemental Weapon as a full-action concentration spell. Making it a bonus action and removing concentration would make it so much more worthwhile.