That's not true, look at this game of Renekton from me today:
http://matchhistory.euw.leagueoflegends.com/de/#match-details/EUW1/2420593570/215011488?tab=overview
I was 6/1 in lane vs TF i believe, as late game came I was dealing no damage at all, was just locked down in teamfights and killed, and ended up being 6/5 from 6/1 in the beginning. The problem is, I was not dealing enough damage to really be useful for damage, and wasn't tanky enough to tank for my team. Also because I had ignite I could secure many kills on my lane and have a good farm early, but I couldn't teleport to help my losing bot lane.