As others have mentioned, useless in melee, but even with a dagger or staff, you were useless in melee.
Just as an illustration of the kooky power of statistics & perversity of d20s, the MU in my very first game of AD&D (@1977) was the only other surviving PC besides my human fighter in the penultimate room of the dungeon we were in. He had a MM spell and a staff, my guy had a 2-handed sword.
And yet, after casting his last spell, HIS staff-swinging dude in a robe did the bulk of the melee damage to the Purple Worm that confronted us. I barely scratched it until AFTER it ate him.
On the main topic...
I didn’t play manysingle-classed MUs in...well...ANY edition, but I tended towards staves & daggers. I did play one with darts that I can recall. His spell selection (I can’t recall what it was) wasn’t great, but his Dex was pretty high. So having darts let the PC contribute in combat.