I mean, at level 9, 5d (4+1) guaranteed damage is still pretty good. Especially for a 1st level spell. I did feel the need to make a 9th level guaranteed hit spell though.
Magic missile can become a lot more potent than that (on average):
Make a Scribes wizard
Take the Elemental Adept feat and pick something that very few creatures are immune to, e.g. thunder.
Change the MM's damage to thunder.
Now you can pew-pew to your heart's content with each pew doing a guaranteed 3 damage instead of 2, and puming the average damage of the pews from 3.5 to 3.75. Not a huge jump, but if you upcast it to level 5 with 7 pews, that's 26.25 on average instead of 24.5 with a minimum of 21 instead of 14.