It's a tough question to answer, and though buffs would've helped, I don't think they would've done much to change a tier list position.
Unless we got more reliable and easy-ish kill setups, we were always bound to be at a low spot. Are kill options are rollout (considered worthless by some, which I disagree with), bair (difficult are very high level play sometimes), nair at high-ish percents, edge guarding (not as reliable for a chunk of the cast), laggy smash attacks, and rest. Rest is the most controversial part of Jigglypuff's placing as I stated before for SO MANY DAMN REASONS!!!!! It deserves a different post/thread. If these were buffed, it wouldn't matter. If we got more kill options, it would've helped tons though!
You could argue that a throw combo would help tons, and I don't think a combo throw would be even 80% reliable at certain percents, and you might also bring up a kill throw, but that would be so broken for Jigglypuff's current throws to change to a kill throw. Throws I don't think would've helped much and were out of the question...
Less lag is probably the second best buff we could've got other than more kill options. It might create more combos, and overall would make things safer.
In the end, I don't think any buffs that we probably would've got in one patch would've helped much, and so, it brings me to closer to my verdict.
Jigglypuff's possible good future never could've been met with buffs... Ever!
So... Can she be mastered? Can she win A NATIONAL?
Theoritically, YES!
But the odds say NO!
Any game can be won, don't get me wrong, but the risk factor of Jigglyouff makes our chances lower in each matchup. The odds of keeping up a good mindset and dealing with the greatest players and winning matches your most likely not going to win are very small. Someone who is great can eliminate many of those bad odds, but the odds will always be against us and with our opponent.
I do believe she can do great things, win tournies, and even compete against the top tier... Kinda. But even a regional would have lower chances for us assuming your region is any good.
She didn't need buffs. Even though it's more risky to play her, and harder to maintain a high rank, I believe her potential spikes among any other with an optimized punish game.
EDIT: I also don't think its the end to patches. I believe we'll get one more justvlike how we got 7 DLC characters instead of only 1 like promised. Don't give up hopes!
Also, Bayonetta and Corrin I think have a chance to be nerfed just a little bit. If there was another patch, I'd guess that they would be changed.