TL;DR: Don’t think too hard about it.
Overwatch is a superhero universe roughly set in the 2070s. The worldbuilding revolves around characters, as they’re made up on the fly. The vagaries of nature and the potential of technology are used as setpieces to provide minimal context to the crazy powers of every Hero in the game, whether it be time bending, necromancy, or Transformers. Most hero abilities fall under the categories of “gadgets”, “robots”, “genetic experimentations”, and/or “time-space anomalies”. Genji, Hanzo, and Zen were the ones that had vague spiritual elements to them, but since they were the exceptions, we assumed that they were the kind of hard-light nanotech you described. With Kiriko’s release, where none of it is given a proper explanation, we’re assuming that it’s probably just magic now. That opens up the new fifth category: “magic”. Fun.
Confoundingly, a handful of Hero abilities are not regarded as canon, and only exist in-game. Despite having characters who can freely manipulate gravity and dematerialize their bodies someone decided that they could not suspend their disbelief for elements such as Lucio’s sonic healing/sound barrier, Zenyatta’s spiritual orbs, and Mercy’s revive. Granted, that last one is probably for the best that it’s not a strictly canon ability, just because a remedy for death is a bit of a quagmire to write around once you’ve invented it. This convention seems to be partly established by what writers choose to depict in Overwatch media, and partly established by Twitter and forum posts from writers.
There’s a few statements out there echoing the sentiment that they go out of their way to keep things vague so that they never feel “constrained” by the lore. Since then, things have gotten even less defined. Take that as you will. It does not help that the lore has been in a state of flux ever since it came out. There was a graphic novel planned to release right around when the game came out in 2016, but it was canned when - you guessed it - they didn’t want to commit to that. They felt they couldn’t deliver. They believed that it was better to provide a loose framework of a narrative for fans to play around in, rather than attempt to tell a cohesive story. I’m not just ragging on the Overwatch team: you can read Jeff Kaplan talk about it himself.
Fair enough. It’s not what I’d prefer, but it’s a legitimate play. A problem arises when things become inconsistent, contradictory, nonsensical, because new lore isn’t being “constrained” by pre-established lore, and Twitter and forum posts masquerade as legitimate worldbuilding. A facade is at least supposed to look convincing from the one side you’re meant to look at it from.
I could keep going, but I believe I’ve answered the question.