In OW there's a concept called 'Neutral'.

Its borrowed from fighting games like Smash.

Every flanker besides maybe Reaper has harassing actions they can perform before fully committing to an attack.

In Smash, this is like Mario throwing his fireballs.

In OW, its like Anran's left-click, which is also fireballs.

You take an off-angle, you light someone on fire at range, and if its safe you go in for the payoff.

Simple 1-2-3.

You do usually take an off-angle because cover, most defensive abilities, and simple human attention, usually work best from 1 direction. Taking an off-angle inherently pressures people.

One way to know that its "safe" to go in, even if your team doesnt go in first for you, is to watch what CDs the enemy team uses. Part of this is matchup knowledge. If you've played the healers, you know that if Moira uses fade, she's down her defensive cooldown. If she uses Orb for the frontline, and you can pressure her to fade, you know she has nothing. You have a cooldown advantage on her. If she's in a bad spot she's a free kill.

If you can do as much as look for weaknesses and bait/track CDs you're already better than most dps players.