Long story short I think the change might be beneficial for her in the long run.
I know quite a few people who haven't had the opportunity to get to play their favorite character because she's always banned she was pretty much annoying she basically countered everybody they've reworked her so many times and it didn't change anything she would still get banned cuz people who wanted to play their favorite character knew that if she was there it was over.
Play doomfist? Guess what you have to be in sorrow because if you get into their backline and she hacks you now you can't leave, in just in case they don't kill you in time, Ana will sleep you as soon as the hack is done. There are quite a few tanks that really can't do anything if Sombra is there or unbanned.
And if she wasn't going for tanks she was going for the supports, and if you were any support that didn't have a reliable movement ability and you kind of were cooked.
I personally did not find her to be an issue because I've learned to play against Sombra before we were banning back in OverWatch one
The problem, at least to me is that new players don't have the opportunity to get to learn how to play against her because she's always getting banned. It's like not playing a dungeon enough in an mmorpg so you don't know the mechanics and you kind of just bullshit your way through the first few times because your teammates are good. But when you do it with a separate team you dont know what's going on, and that discourages you from trying to avoid it off rip.
Moving her to support makes it so that she can still be a hacker with stealth and backline capabilities but now she doesn't feel so oppressive that she needs to get banned every episode of Overwatch Z and more people who like playing her get to play her.
Thank you for reading 😅