"Suffers most" has to be topped by Fighter, as whatever special thing their weapon does it will eventually do it up to 3 times per turn (or if you got to level 20, 4 times), and more if they action surge. Also the powerhouse fighter builds use their Fighting Style and extra feats (assuming you play with those) to specialize in particular weapons, so in a campaign where magical weapons are limited in a way such that they are less likely to find the one they want they suffer on that front. Dex oriented Fighters suffer most here, as they have a substantially more limited subset of weapons available to them.
But see, like most folk my mind went straight to magic weapons, as being the type of magic item that seems a bit obligatory to distribute. This is why I recommend considering the possibility of making low level magic weapons fairly common or even ubiquitous and just not really having much magic swag beyond that.
You can also give out suboptimal-to-their-build weapons with a low level enchantment. I had a glaive oriented polearm master at one point whose only magic weapon was a quarterstaff he would get out when he suspected resistance to mundane weapons. The big loot can be getting the low level magical version of the weapon they actually want.
That said, depending on what you consider a "found magic item" the Wizard may be the most put out, given that they are the class built around the assumption of finding some spellbooks and magic scrolls and that stupid special ink to copy them with.
Also I would note that, while the Artificer is the class that is designed to provide their own magic items, in a campaign with few magic items this may mean they really get to shine by being the only one decked out in magic bling, really get to shine by providing for the needs of the group, or feel put out because they need to spend their infusions dealing with group needs. It really depends on the player.