I never considered reach the problem - something with a lot of reach should be dangerous to approach.
There were, however, serious problems with how stats, well - Strength really, modified with size in 3e. Each step up from Medium, when designing monsters, was +8 for Strength. That made them grappling gods when it came to grabbing a PC and hampering them. It also meant that, in at least some cases, there was a widening gulf in effectiveness between melee and ranged attacks - which made giants kind of weird. Up close, they packed a nasty punch, but one of their big threats from 1e/2e was throwing big rocks so that they were a threat at range too. That wasn't really true in 3e because their Dex stayed flat or got worse based on size (compared to someone smaller) while their Str skyrocketed - kind of unbalancing their traditional role in the D&D adventuring universe.