There's always a point to shipping regardless of canon status, I think CA shippers just want their ship to be endgame and that's understandable.
No promises to keep is very complicated for me, personally, because I don't interpret it as being just about Cloud. The song is a journey and Aerith cries at the end of it, which is strange because if it was about Cloud why is she crying? He's literally right there watching her, but she ends the song looking out into the crowd as if searching for someone that's not there.
She also writes the song after Tifa tells her that Cloud has remembered Zack after all and they were actually friends in the end. I think it does a disservice to say NPTK is just about Cloud as much as it's a disservice to day its just about Zack. In fact, the song is really similar in feeling to her farewell monologue from the FF 30th anniversary exhibition in 2018.
"I hate the sky, it carries away everyone I Iove.
Stamp… Stamp! Guess, you’re gone too.
‘With a new love, you’ll forget the old one.’ I’ve heard this story before, but… is that really so? Is it okay if my heart hurts?
This is a strange place. Flowers bloom all year long. The seasons never change–my feelings never change. I’m stuck.
Sometimes I see someone who has the same eyes. Same as you, I mean. And I wonder, should I ask: do you know him? do you know where he is? But I never do.
I know goodbye will be hard. But when I think of meeting someone new, I still get so excited. It’s cruel.
Things won’t last forever. Sure, it’s lonely. It’s sad. But I can say "bye” with a smile, right?
That’s it. I give up! I can’t stop thinking of you. Ugh, I can’t stand this!
Helloooo~ Wake up. It’s almost morning.
Don’t step on the flowers!
You came. Thank you, I’m glad. But you’re already….
You’re so far now. I’m so far from you. Oh, I’m rising. The sky is carrying me away. I can see you, you’re crying. Don’t cry, you’ll make it rain."
Personally, I don't think we can look at this monologue and say it's just about Zack, the same way we can't look at NPTK and say it's just about Cloud. These are Aerith's canonical feelings for both men and no matter how we slice it, Aerith's feelings for Cloud cannot exist without coinciding with her feelings for Zack--even in the OG.
But that doesn't mean people can't ship them, they just have to be realistic about the kind of content they're getting. As Aerith plainly says in her monologue, she's not able to get over Zack even though the thought of meeting someone new/falling in love with someone new excites her. The idea excites her but she never truly falls and as she says in her own monologue, she gives up on trying to replace him even though it frustrates her that she can't.