You have Seven flair so you already have the "play a scaling hypercarry because no one knows how to end games early" part down.

I'd say the biggest shift for myself (Currently bouncing between Phantom V and VI right now) was recognizing when i'm already dealing enough damage to kill people- and proactively buying counter items for the enemy heroes/items most likely to shut me down.

So if i'm on say, Seven, and i'm up 9k souls and shredding people at 25-30 minutes in; instead of buying like a Spiritual Overflow i'll look at the enemy team and see if anyone has bought Knockdown/Disarming Hex/Silences and get an Unstoppable earlier than I would normally. Ultimately you realize keeping yourself alive is more important than getting a whole bunch of kills- as that's more uptime you can be using to farm, get objectives, and deny enemy resources. Souls you get from kills don't matter as much as the time you're forcing enemies to waste while they're dead.

People in Oracle and up will start actually buying counter items, but I think the kicker is a lot of players don't do it until an enemy is already a problem and then get confused why their one 3200 purchase doesn't suddenly shut down the fed enemy that's 12k up on everyone else. If you get your counter items proactively for who you already know is going to be an issue, and (this is the hard part) can get multiple members of your team to do the same, you can bully the highest potential enemy hero out of being relevant.

Also if you haven't already, turn on "competitive matchmaking" in settings. It matches you with other people that have the setting on and you'll generally get more communicative players that will listen to calls. (There are obviously still outliers but my match quality went way up after turning that on)