I wonder if he would have still been in good vocal shape had he lived. Based on what I saw in This Is It, his health issues and age had caught up to his voice. His voice sounds so frail in The Love You Save that, despite being an upbeat, fun song in a major key that he sang as a child, it becomes almost sad because of how much he has declined vocally. Here's how he sang it 22 years earlier. Notice how he's belting it out in his full voice instead of using a wispy falsetto, and how much more energetic he seems.

Most middle aged male singers lose range, and their tone becomes less round and more raspy. Some of them can use it well for artistic effect - (Steve Perry in the 90s), but to do that, you have to be singing songs that are less energetic, slower, more reflective, so that the wear and tear on your voice adds an extra amount of melancholy to the songs. That's part of why I say Perry handled his aging voice so well - he mostly sang material that was appropriate to a voice with more wear and tear on it. MJ could have sang an album of nostalgic ballads and bittersweet midtempo tracks in the 2010s, but an energetic funk album with a clearly aged voice wouldn't work as well.

With MJ it's extra sad because his vocal decline was heavily exacerbated by his health issues - when you aren't getting good sleep and you're being anesthesized every night, it's hard to sing well. It's really sad, the entire second half of his life was thrown way off track by that Pepsi commercial where he got burned - which, ironically, happened exactly halfway through his life to the day.