as a Raiders fan, I can't really say how great of a talent Jamarcus was or wasn't though, but you best believe that his arm had me excited.
I was riding with him the whole first year he sat out for most of, I was saying pay that man, but dude definitely is a cautionary tale. I'm not even putting it all on him, he was a young rich guy who clearly let his food/substance/personal demons get the best of him, but he wouldn't be the first Raider player of the last 20 years to show up and not give a fukk lol.
I'm not sure bad is the right word, I would go more with disappointing because quite frankly i'm not sure we know what he'd have been with his head on straight. so saying he was "bad" speaks to his talent to me and I feel like we never even really got to judge that one way or another properly.