One of my players (magic-user) has subtly complained about not being able to do anything and feeling useless, how should I address this?

So, first off, he's playing a Magician in a Dolmenwood campaign, he just hit level 4. I keep telling him there will eventually be a payoff, but we've gone through 1 large dungeon and 3 small ones at this point. Dude is a great friend of mine since childhood, there is absolutely no interpersonal conflict between us. This is not a "talk to your player" problem.

Here's some things I've heard him say or mention recently:

"I'm a magic-user, so I can't do anything this round."

"I would use a spell here, but I don't know any, and we should save it for Sleep anyway."

"I'm not even going to throw a rock because I have like a -4 to hit."

"Being a magic-user is objectively worse than being a wizard in modern systems. There's no cantrips, but it's still somewhat satisfying to sleep a horde of enemies. It just rarely happens."

And so on. I should mention, he does like the OSR playstyle, completely gets it, and he knows he has to think creatively. But I think he sometimes just wants to blast monsters, ya know? And sitting there watching the fighter run up and 1v1 tough foes while the cleric incinerates a horde of skeletons with turn undead... Yeah, I can kinda see why.

And to address some of his problems, he has found plenty of spells to learn, but most are situational, and he's always under the assumption Sleep is better so he's afraid to use up any slots.

He is a Breggle, and can use his horns to attack which are better than any weapon he can use, but he is playing it smart and safe and does not get into any melee combat.

Basically I am looking for suggestions on how to handle this perceived imbalance (I am aware this is the nature of being a MU). But at the same time, I just want him to have more fun.

Should I let him learn a cantrip? Give him magic rod which can cast a cantrip? How would I even go about designing a basic cantrip? Save vs. Spells or take 1d4 damage?

And for what it's worth, I have allowed him to change classes, but he wants to commit to MU. I think he's trying to power through it.

Any ideas would be really appreciated!