Here would be my point: can you make the argument in good faith that he’s NOT pining over Aerith? Why keep it so overly vague? The fact that Cloud was actually happy in his situation with Tifa and the kids now feels so empty because Nojima and co went out of their way to show all the low points in their relationship and left all the high points to the viewer’s imagination. I’m sorry, but Cloud is a poor partner in ACC, and him even potentially pining for Aerith adds a whole new layer to the shit cake.
Proposed past context of romanticism ≠ pining, if said character (or person) is feeling something from their death. It would be a hard hill to say that this was vague considering what has been expressed and said in all supporting material.
I'd say it's easily a good faith argument, if even rather a strict one, because it's what is supplemented by the plot and other paratextual materials, in either a proven way or that of logical connection. The "pining" action comes from an audience perspective of
Cloud wanting to be with her romantically and lamenting that he can't because she's dead (which, has it's own split differences from just
having any amount of romantic feeling)—both of these things aren't firm to believe in the most adamant sense (hence two decades worth of argumentation, most likely), but also, the specific
proposed character motivation that is blatantly being said here is literally not what his problem IS, and this isn't expressed at all in the story. Guilt, regret, low self value, and moving on from past events—the deaths of Zack and Aerith and suffering from Geostigma are pushing THESE emotions and lead his actions, and are the only things that have been described within the actual film and supporting materials.
Now at best, if in good faith with believing Cloud did have any amount of romantic feelings for Aerith (again, slightly different the specific motivation to be with her through pining)—you'd be just saying that Cloud has been affected very heavily by the loss of someone he had romantic feelings for. Simple statement—which is
not the same as saying he's currently pining (i.e. actively wants to be with her) for her because that depends on a numerous lines of conjecture that can't be backed up reliably. This is a big step away form the reasonable thought of Cloud having romantic feelings for her during the OG. It would also be reasonable to understand why Tifa would feel mixed feelings about Cloud's emotional degradation from Aerith's death (which is supported by the movie + supplemental material), because on paper at glance, your partner feeling anything for someone they felt any amount of romance for is a "no-no", but the reality of their situation (and how it works in real life emotions), should in good faith, allow all the information saying it's about guilt, regret, low self value, and moving on from past events, as a true answer as opposed to Tifa being sad because Cloud wants to be in love with Aerith instead of her, which isn't presented in the story or supported materials.
Media begets interpretation, so I'm not surprised that this is one of many interpretations out there. It's just that when you get to the nitty gritty, it's simply a non-component of the story outside of one's knee jerk interpretation. Whether they played OG or not—people's surface level understanding of relationships can easily trigger this interpretation about what Cloud is feeling in AC. Understandable, but step further in, and it becomes less so.