Hmm...I see your point. Any advice on how to fix it?
Well, that depends mostly on whom the spell is supposed to counter.
For what it's worth, it sounds like it was supposed to take out brutes and soldiers (you know the monster roles), but I could be wrong about that.
My first thought was to make it deny reactions, but that made me realize that Slow also existed.
The next idea was maybe the saving throw penalty, but that's basically just Bane.
Then, I thought about how to expand the fluff of what the spell currently does: Why not make the creature deal half damage (as if the target of the affected creature's attacks had resistance to them?) But that's Ray of Enfeeblement.
So for now, I am leaning maybe: "The target does not gain the benefit of resistance against weapon attacks."
Kind of niche, but also really good for when your party really needs to take down a lycanthrope (or something like that) at low levels. On the other hand, those kinds of creatures tend to have better than average constitution scores so it is still risky.
Also here is a spitball for the spell name: Nemesis