I feel like this was made SPECIFICALLY for parties that over use magic missles/wand of magic missles. hilarious lol

My level 5 warlock is wearing this... really shouldn’t require attunement 

Maybe make a homebrew version of it that does not require attunement?

I think attunement is perfectly balanced. You are putting on an item that reduces a whole damage type and permanently protects you from the only spell that never misses. while yes I would of liked more from this I think if enough of your enemies use force damage this is worth while.

this don't seem bad in anyway. could have been a little more interesting but honestly it isn't all that bad.

Very useful on Warlocks who don't want to spend their high level slots on Shield. in general being immune to the potential 3+ DC10 concentration saves will keep your spells active when fighting wizards or magic missile users.

If fighting someone with this broach, other multi hit spells like Scorching Ray, Jim's Magic missile, E-Blast, Ice knife, Tasha's caustic Brew, and others  things like multiattack will be desired. more so if they're not force damage.

I play a Graviturgist in my friends Wildemount campaign and I use Magic Missile frequently to force movement from the level 6 ability. My DM can't find out about this.

This could be reflavored as a belt buckle, a ring, a headband, a bracelet, a cloak...

Strahd Von Zarovich's cloak is strangely resistant....