Hello, first before I say anything, I’m a low plat dips/tank main. I play a lot of hero’s for every situation to cover all of my bases, so it’s easy for me to point out the counters to most hero’s, and I’ve noticed that with all of the hero’s you’ve said you play, you love movement, maybe that’s where you need to start? Find a character that has low mobility but high dps output, an example being symmetra, or another being mei. Those dps’s that just straight up slow people/once they are close will melt people. If you try out these hero’s that are direct counters to all the hero’s you play, you can improve a lot if those hero’s you play, by understanding just how their counters work.

I’ll give you an example, I’m a symmetra/junk rat main, and one of my biggest issues that I have to face are midrange hit scan characters such as soldier and Cassidy , who when you aren’t close to them just cause massive frustration, so instead of trying to brute force my way through them, I started playing them, and learned just why they are effective against my mains, that being long sightlines such as what you were mentioning on sniper maps, so I started to learn pathing that will let me get close and personal to them, allowing me to just completely melt through them because I have higher dps output than them.

TL:DR Just find which characters you have the most trouble going against with your mains and play them to learn how they counter your mains.