High damage alone can “kind of” create space. But not in a traditional sense that tanks do. Also, with just high damage, like with snipers, the way it “creates space” is by making the enemies hide behind a corner/wall, so that they don’t get one shot. I don’t think that’s the kind of space making we’re talking about when it comes to Overwatch.
There are however squishies that make space similarly to tank do using their survivability and damage mitigation ability. Like with genji, venture, and similar heroes. It’s just that tanks do it better because they have the damage of DPS in close-range (threat), and health pools to keep the enemies attention to them for longer.
Which helps squishy roles like DPS and supports to get focused less often. Which leads to the type of team-fight that we want out of Overwatch. If the game was just DPS + Supports with 200HP, I think the team fight would end very quickly each time and the TTK would probably end up becoming more like Valorant/Counterstrike.
Recent global health increase to 250HP for squishies partially helped lengthen team-fights, even when the tanks are dead. But I still think we need tanks unless we start giving DPS/supports more tanky heroes to absorb all the damage.
So to recap, I think for squishy heroes to “create space”, they need to have at least one or more of the qualities such as high mobility (like tracer’s blink, genji’s dash) + damage mitigation ability (like genji’s deflect, Venture’s Burrow, Reaper’s Wraith Form, Mei’s Cryo-Freeze, etc).
Genji/Venture/Tracer’s fight amongst each other would last fairly long, thanks to their “pseudo space creating abilities” which allows their fight to be taken in an open battlefield. But Cassidy/S76/Widow/Hanzo/Ashe fighting against each other would result in Valorant style of gameplay.