It's definitely not as bad as it use to be. Renekton use to be worthless in any game that went past 20 minutes, now he can actually last longer than that.
He also works better in certain comps that others. His AoE armor shred on top of building Black Cleaver can open up AD heavy comps to do a lot of damage to an enemy team and he can also quickly get through a front line to lock up and harass the backline.
Ideally, his playstyle is best to quickly pressure top lane into taking the tower down early which then frees him up to assault other lanes with his early game presence which allows your team to gain momentum and then(ideally) do all the work late game as far as damage goes while Renekton becomes more Utility based as the game moves along.
This is just general information. Im not a Renek main or anything, though I would love to be. He's a fun champ with a lot more potential than he use to have outside of eSports use