First, she wasn’t broken at lower ranks. Her winrate was stable across all ranks. Overbuff still have stats from pre-rework Sym if you filter by six months, you can check them per rank and see it yourself. If you have other sources that state the opposite and are not anecdotal, be my guest to present them.
Second, I did a very extensive list myself of how to buff Sym2. I know pretty much every Sym main at the time also had a personal list of desired improvements.
But the biggest issue was not only that the change was drastic. It was that the devs never ever tried to tweak Sym’s kit before going for the sledgehammer.
Take, for instance, Roadhog’s hook. It went through a dozen hook “fixes” that didn’t solved the problem, and then they finally gave up and just reduced his weapon base damage. Soldier had three adjustments in his pulse rifle damage to reach the spot he is today. Mei and Reaper, in the patch directly before Sym3 rework, received small adjustment buffs to their kits while retaining their playstyles.
Symmetra never got that. Had they tried a few things before going for a full kit revamp, it would give a lot more weight to the “old kit couldn’t be balanced” argument. As the situation stands right now, we can’t take this argument in good faith simply because the devs never tried to balance Sym2 kit.