the disparity of scope between full casters and everyone else is highly jarring. for the most part you're either a sword-swinger (or slightly glorified version thereof) or you're telling reality to sit down while the adults are talking.
classes on a conceptual level. some, like the wizard, are supposed to encompass a wide variety of character archetypes while others, like the barbarian and monk, are pretty obvious in what they're going for.
feats are a mess, conceptually and in practice. they cover a wide array of things from simple skill ups, making certain assumed normal techniques useable or opening entire new uses of existing resources.
skills are too granular and most characters don't get enough points to be seen as skillful. it also takes a while before you get your skills up high enough to be successful with a good consistency.
weapons as a whole are pretty boring, with them basically just being a venue for dX worth of damage. the weapons are, for the most part, a slight variation of damage dice, damage type and weight in any given category.
magic doesn't really have a limit or any real concept beyond some superficial elements and how it's cast. stuff is often either extremely mundane or magic and magic seems to be capable of doing anything and everything with a little tinkering.
magic items, especially weapons, don't feel magic. a slight bonus to your hit and maybe a minor damage effect doesn't really make it feel "magic" then again, i grew up with the mythological stories of Excalibur, Mjölnir & Caladbolg.