Just because you respawn doesn’t mean one-shots are healthy. Sure, you respawn but you’ve already lost the team fight, so who cares?
As for games in which you don’t respawn, oneshots are often more key to the game. Rainbow six siege was mentioned earlier. In that game everyone can one shot. Everyone. The difference is the player skill. One shots are woven into the foundations of the game. This isn’t the case with Overwatch. Overwatch is built around long team fights and we know this because we have tanks and supports whose entire function only exists to create extended team fights. In such a game, one shot mechanics are very powerful, and need to be balanced with draw backs.
Let’s look at other one shots. Self Destruct. Anyone complaining about self Destruct one shots? No. Why not? Well, because it’s a highly telegraphed ability that is tied to an ultimate so it comes up rarely and has significantly counter play. Also, she has just jumped out of the mech, temporarily taking her out of the game leaving her vulnerable to kills or to being cced out of her call mech.
OK, what about Rocket Punch? Well, it’s a tad more contentious but still mostly accepted. Why is that? Well, it’s is also telegraphed as it can be heard half way across the map. It also has a long cast time and leaves Doom vulnerable for the duration, so he can be stunned or slept or the teammate can be protected. It also puts Doom into the whole enemy team, so it carries risks, and is tied to a cooldown. Risk, reward, and cooldown keep this one shot in check.
Widow? Hitscan shot that oneshots most of the cast with no telegraphing, a tiny cooldown if we even count the spool up time as a cooldown and no risk. She sits half way across the map, out of everyone’s effective range and has a shorter ttk than everyone she fights against.
These 3 one shot abilities are not equal. I’ve noticed you like to use the word disingenuous, and that’s exactly what your claim that people objecting to Widows oneshot is just anti-one-shot rhetoric is.
The most similar to Widow is Hanzo, who has one shots with basically no cooldown, but he at least has to deal with drop off and travel time, and his ability to escape isn’t quote as strong. He has a lunge and his wall climb, but Widows Grapple is much faster. Also, while Widow is grappling high into the air, she can shoot back but Hanzo can only shoot back during his short lunge and not while wall climbing. Also, Hanzos hitbox is a lot more forgiving.
So, ultimately, Widows oneshots lack proper counter play. She can distance herself from flankers through grapple. Firstly leaving herself harder to access, but also pulling herself into the air to temporarily separate the two players and give herself an easier shot. Her shots aren’t governed by a proper cooldown, aren’t telegraphed, and are very consistent, being a Hitscan shot. The only counter play is to have a a better play use the same character and beat her at her own game. Overpowered or not, this is just bad hero design, and that alone warrants a rework.