As demonstrated by an Udyr vs. Lee Sin game I just had.
My Irelia top died at level 2, while I was on my way gank. I killed the enemy Renekton in response, held the wave so my Irelia could freeze, then recalled and immediately headed back to top lane so I could get her ahead.
The Irelia was a low level player. I assumed they were a smurf. They weren't.
I ganked again, but she didn't wait for my stun, missed her stun, accidentally Q'd a minion, and basically didn't touch Renekton. He got away with a sliver of health and had to recall, but I also took a lot of damage and had to recall.
During this time, my mid laner dived for a kill, and Lee Sin killed him and cleared the wave. He then went directly to bottom as my 3-0 laners also tried to dived, got a second kill and shutdown gold, and cleared the wave again. **He's now 2+ full levels ahead of me from soaking lanes and the kills.**
I'm completely removed from the game thanks to the top laner's misplay. He's 24/7 invading me and I'm unable to contest, which puts me further behind and prevents me from really impacting the game. At one point, he was 4 levels ahead of me.
These pre-season jungle changes are just going to make this entire scenario worse. With less jungle EXP, he would get even further ahead from soaking the waves. The jungle needs better come back mechanisms and less reliance on lane performance to remain relevant.