They could have made it even worse. They didn't say why Aya passed away at such a young age. Let me spin you a story:
Since she obviously didn't make it big time and only played a single concert in a shady club in NY, she got disillusioned when hear dream didn't come true. She found solace in drugs and an abusive boyfriend who pimped her out. One of those customers beat her to death in a drug induced rage when she tried to steal some of his drugs for her own addiction. The club owner only has her guitar because she pawned it off early on. As to why it was special to him... he was the boyfriend how pimped her out and he's remorseful for indirectly causing her death. 3 days after Fu brought back those memories a he gets found by those band members we saw in the episode with an overdose and a suicide note saying just "sorry". And it could all have taken a different turn if only Fu had confided in Aya back then.
No, definitely wouldn't have made it better. But I still feel unsatisfied with such an important point just omitted. Aya died in her mid 60s so there could have been a lot of possible explanations given for her passing, but at the same time it's young enough that I am left wondering what the reason was.
Mayonaka Punch is an original anime story, so let's say Aya last performed 2 years ago from the present, i.e. in 2022
The wider looking person in the video, whom I assume is the bartender who Fu meets, looked much younger in the video, so Aya probably had something of multi-decade a singing career.
It doesn't say whether she was a superstar (unlikely), or an itinerant singer who sang in bars part time, or something in between, but there's no reason to think that Aya gave up singing until whatever caused her death caused her to do so.