This reminds me, I also dislike the idea the Cloud and Aerith are star-crossed lovers.
First, never mind the fact that stars are a Cloti motif, where does this idea actually come from (from Aerith dying obviously, but there needs to be more reasons to argue that feeds into a star-crossed lovers premise rather than creating it)? I would argue that everything fell into place perfectly so that Aerith and Cloud went on a big adventure together, and that there are way more obstacles for Cloud and Tifa to overcome than Cloud and Aerith.
Almost from the very start to the very end of the compilation, Cloud and Tifa face numerous obstacles that prevent them from connecting properly. Cloud and Aeriths "romance" can only happen in a situation where everything has gone to shit, Zack is dead and Cloud is emulating him. Had Aerith not seen Zack in Cloud would she have ever given him the time of day to get interested in the first place? I honestly can't say.
The only thing keeping Cloud and Aerith apart.....is the fact they love other people.
Star crossed lovers romance to me means two individuals who fell in love with each other and cannot continue their love story due to circumstances out of their control. This seems to apply to Aerith and Zack because they both fell in love with each other but couldn't be together because Zack dies, Aerith does not get closure and then she eventually dies. Aerith still yearns for Zack even after his death. And Zack's last thoughts were Aerith before he died. Its tragic for both because they are in each other's heart but couldn't be together.
EDIT:
In rebirth, not sure if its intentional but the visual storytelling of the ZA scenes alludes to star crossed lovers:
-A "dead" Aerith in Zack's arms as he mourns her while it starts to rain (gives off Romeo and Juliet vibes)
-Zack carrying Aerith in his arms
-Zack touching Aerith's hand and Aerith feeling it in the LS
-Zack saying "hello in there" to sleeping Aerith (looks like something out of a page from sleeping beauty (the prince returning to his princess)
CA doesn't feel like star crossed lovers because it wasn't a mutual love story. And even if Aerith had lived, I do not think it would work out because Cloud loves Tifa. For Cloud, Aerith's death is a tragedy because he could not save her and and has to live with that guilt.