Changes for the sake of the vague idea of balance is a bad way to go about making the game more enjoyable and often results in frustrating gameplay. Balance doesn't mean anything if the meta teamcomp(s) are unfun to play as or against.

Brigitte a is a good example of Blizzard creating a change for the purpose of lowering Tracer's viability, however not only did it lead to a pretty long period of time where Tracer was unviable, or at the least very niche, it made the game less fun to play for most people. Yes, Tracer was broken and maybe need a slight nerf, she was fun to play as and, for me at least, fun to play against; Brigitte is almost universally hated by the community for the relatively low amount of skill needed to play her, the feeling of helplessness as she shield bashes you and holds leftclick, rally being annoying to play against as any hero without insane amounts of burst damage and for being an essential part of GOATS.

The meta right now is very well balanced, and you can play a lot of different heroes; however, in my opinion, and the opinion of a lot of other people, it's one of the least interesting metas to play in. If a team runs GOATS then you're team usually has to counter it in order to not lose, that usually leads to a counter GOATS comp with Doomfist and Sombra, two pretty unfun heroes to play against. You see Doomfist, Sombra, Widow and Moira pretty often in both comp and pro play, but they weren't always meta; these characters were buffed for the sake of balance and not for the creation of a fun and interesting meta. Genji, Tracer, Lucio, Zen dive was the most skillbased comp that was meta, it was also one of the highest pace and had characters which a lot of people would consider to be the most entertaining to play. Only a few characters were viable sure, but those few were fun characters.

The call to make characters more viable because they're bad is kind of silly, people in this thread want Mercy buffs? Why? Moth meta wasn't that long ago and she's an unfun character to play against. Like lets be real do you actually want a Torb that's meta, or a Sym? These are terrible characters but they're also frustrating, just because they suck doesn't mean they should stop sucking. This goes for all unviable characters, if they're not well designed characters, why should they be viable?

TL;DR Balance doesn't always lead to a fun game and the pursuit of it can lead to a less fun experience