What's Winston's role anyway?.
To isolate enemy team members and create a safe zone where his DPS can move through to the isolated targets. More defensively, his job is to be able to discourage fighting by threatening cramped zones with AoE damage and bubble isolation.
Let me lay down a scenario for you: Wisnton jumps on you, a 200 health hero in the backline, and drops his shield. You are dead in 3 seconds to DPS unless Winston is dead or that bubble breaks and you get help. So now it's a DPS race and Winston is probably going to lose because let's face it his DPS is rough. But let's introduce some what ifs. What if Winston jumps on you while the rest of your team is ain a team fight and you have to solo race his DPS? Can you always win? What if Winston placed his barrier in a way that still isolates you and protects himself, effectively making him have hundreds more HP? Can you beat him then?
What if Winston's DPS players use the space he created to move in on you and kill you faster?
What if that DPS was Tracer or Genji and you ate 300+ burst damage instantly while being isolated?
What if you had a discord orb on you and died 30% faster?
What if Winston had a bubble on him making him briefly immune to CC with an added 200 HP?
What if Winston's team was moving too fast for you to react to?
That's what a dive comp looks like, and all of that will happen in roughly 3 seconds or less. You die, hell maybe somebody else dies, and now you're down people and the enemy team has a small fort in your team's space.
"But Anne, good teams will just instantly focus the Winston"
Okay, let your Rein turn to look at the Winston while the enemy team dumps every offensive CD past his shield. Let your Zarya turn to help you while the enemy team just murders your Rein. Let your DPS focus on Winston + bubble while Genji or Widow or Tracer calls them out for not paying attention. Best case scenario is Roadhog gets a hook or McCree gets a flash to cripple the dive, and that's rough. You have to hold things like Ana nade and preemptively position around things like this.
"But Anne, that requires a fantasy land where people work together."
When I booted up the 6v6 team game where people have to play unique characters with unique abilities that synergize to form a better whole, I made the assumption I would have to rely on others to really maximize what I'm doing. I also had to concede sometimes they would let me down or I would get a bad read on what my team is doing and fail.
The simple truth is that Winston requires a bit of planning and coordination to work. Just a bit. Like literally "go to where I go and shoot things near me" level of coordination. And the truth is the average Overwatch community isn't quite there. Yet.
So a solution I hear tossed around is "make Winston rely less on others then" but frankly that's just shitty and bad design. Winston dives are very satisfying to pull off and show some degree of coordination. There's a skill curve and something to like work on getting better at. It's a team game. Some characters work better with a coordinated team and excel wildly when they have that. Others can excel on their own. That's just the nature of things. A character rewarding good teamwork is a good thing to have in a game that emphasizes teamwork. Making him just flat better when he is already well balanced and fun when used correctly is just going to throw off that balance and move him away form something that already works for the sake of rewarding people not putting in the effort. No offense, but this is a competitive multiplayer game, and if you aren't going to put in that effort then frankly some heroes are just going to be off limits to you because of your own skill level.
Anyways, yeah. That's Winston's role and how it works. Idk, go try and use him like that and see what happens.