Gangplank needs a massive adjustment in how utterly fail-safe he is.
And I know people will probably flip out but let me explain before you throw downvotes.
I have no issues with gangplank being safe. In fact, he's the safest pick in the game. There is almost no lane where he can't just simply elect to not interact and farm in. There's a few issues with this. For starters, he's one of the hardest scaling champions in the game. Once again, I'm not bugged by this though. I'm more bugged by all the extra gold he ends up getting when farming with Q/E. I know this has been his identity for quite some time but honestly, it's what makes him so utterly impossible to shut down.
Once he gets trinity force, he's a huge threat. It doesn't matter where he stands because that trinity proc on barrels hits hard no matter what. His ult is good, even without an upgrade. But once he farms out an upgrade, you simply cannot fight gangplanks team when his ult is up. I've had games where I've gone 0-5 in lane and I come back 10 minutes later after power farming and end up getting 4-5 kills right back and doing the most damage in the game. It doesn't matter how far behind you get on him, his extra gold is just going to make up that difference and with how quickly he can clear waves with his barrels, he farms mega hard super fast.
This is my biggest issue with Gangplank. It's not that he farms hard, it's not that he's safe, it's not even how he can bully several laners - that's all well and good because he's scaling is mostly dependent upon him picking between bullying and farming. When he bullies, he's not farming as hard so you still have a chance to kill him. When he doesn't bully and elects to farm, you get a free lane. What bothers me is that you can't shut him down. It doesn't matter how many times you kill him, he's going to just farm it back at a pace you can't keep up with. And that's why I said he's too fail-safe, he's always relevant. And for a champion that scales as hard as gangplank, I honestly think that's a pretty big problem.
Before anyone comes and tries to say he's garbage, check champion.gg and see how he's in top 6 winrates in both mid/top, with a total playrate of 18%. Not to mention, he has remained the most efficient pick in both lanes since he's basically been meta. In short, he's one of the best champions in the game still despite all the nerfs he has received.
I honestly think he needs to lose his bonus gold passive on Q. It was added on old gp along time ago when he was complete garbage and it made sense then. It doesn't really make sense now.

that build triforce and tank everything triforce just adds so much omph to abilities that proc on hits that gp barley touches crit builds anymore but again thats just me and my hate for all non lichbane sheen items