Oh, alright.
Frankly, I can see why most people think Gnar sucks - he's inconsistent as shit, which is why he'll probably never be used in competitive play. There's also the fact that Mini-Gnar and Mega-Gnar are effectively two completely different champions that require two completely different build paths and two completely different playstyles, people would need to have ample knowledge of both AD Carries (Since mini-gnar pretty much plays as one) and Tanks to play him effectively and find a way to give both forms exactly what they need (which effectively means build bruiser). There's just so many things about gnar that are in opposition that it's hard to wrap your head around, so yeah, I can see why people say he sucks.
(And even when you do know how to play him, there's still the fact that he's just inconsistent and counterplay against him is really easy - don't engage when he's at full rage, so yeah.)