Just look at this logically. Before Brig came out, GOATs still existed. It was not a problem, because it was a very specific comp that could be countered, and was used situationally, as comps should be. At the time, the triple support was typically Lucio, Zen, Moira. It was not an overbearing comp. It could take a team by surprise on a quick offense because ti was overwhelming. And so, on certain maps, it was a good choice to take Point A quickly. A popular enough option if the team only needed to get point A quickly, but also coutnerable if predicted or had the time to swap. That is the concept of Overwatch. That was fair.
Then Brig came out. Now GOATs is overbearing. Now the only counter to GOATs is GOATs. Other options exist, but are clearly not reliable enough to be used. That is why Contenders is almost all GOATs at the moment, even with the recent Brig nerfs. The problem still lies in Brig.
Lucio, and Zarya are, imo, perfectly fine balanced. I do think DVa needs slight, small tweaking so she is not so useful in all situations, but that is not the problem with GOATs. The problem is still Brigitte. Nothing needs to be changed about Lucio or Zarya. If they were nerfed (and Lucio just had to recieve a buff a few months ago because his ult was such garbage), they would have no play outside GOATs. That is not balance. Look at Zarya in OWL; the only times she has been reliably used are during Hanzo meta (specifically just for her ult combo), and now during GOATs. That’s because professional players -the best playerpool in the world- are very good at not shooting Zarya’s bubble, so it is hard for Zarya to retain charge. In GOATs that is out the window, because the entire match is a brawl on points. You can’t miss her. If she was nerfed I doubt it would do much for GOATs, tbh, as I have seen it run just fine without Zarya, but she would be a trash-pick in any other situation as well.
The solution is that Brig still needs minor tweaking downwards, particularly in her self-sustain. A support should not have that much self-sustain. The devs said it themselves when they first reworked Lucio and specifically nerfed his self-sustain. That, in addition to looking at the heros that should theoretically counter GOATs (Reaper, Hog, Pharah) would help put it back to a situational comp.
The problem lies in that if you buff those counter-heros to counter GOATs better, a different fire may well be started in that they could be too strong in general elsewhere.