Get better CS, you're getting about half of what you could. Even on Nasus.
Know when your characters are at their most powerful.
For example: There is a wrong assumption that Nasus has this godly late game.
He doesn't, he gets kited and exploded by DPS late game.
Look for how you're doing on Nasus for example. If you're at 500 stacks at 20 minutes with
, then you should really look to start ending the game because you're at your strongest and any longer will bring your opponents closer to you.
For example: If you're stomping on Garen, let them watch you farm, and get every single CS while your minions die to theirs or their tower. Push turrets. Kill villains.
It looks like you like juggernauts. Honestly look to essentially win the game by like 18-25 minutes. Your characters are not for late game, and you shouldn't let late game happen. Be strong when your characters are strong and win the game at that point, rather than hoping you'll continue to be strong.
If you're getting similarly fed and farmed as the enemy ADC or whatever, there is still a point where you will stomp them because you just out-stat them and your items are more efficient at that point. Don't let them continue their spree against your allies if you can help it. Just sit on them and make them pay with your strong early/mid game.
But seriously, if you're ahead in lane, go for CS. Watch any "I played Darius in low Elo, this is what happened" video. There are a surprising number of them ( Here's a good one ). They get fed AND farmed, and that huge disparity of gold wins them the game. That goes for any character you're playing top.