I think it may be the level of "film grain", as well as a bit of glow around the buildings in the sky, both are a bit too high admittedly, I honestly just liked the look of the shot with the added grain and I've just started getting into photo editing so I'm still not too great at it. I probably should've put some sort of disclaimer in the description that it was edited rather than an actual film photo. I do have some old 35mm point and shoots and even an early 80s ricoh SLR I just got, but haven't gotten to use them quite just yet, my first film roll is supposed to come in in a few days so I should hopefully have some actual scanned film photos coming in a couple months or so.
The grain in the sky is too much. If you zoom in, you can see yellow grain like flicks of glitter. Real film doesn't do that unless there's something atypical.
Here's a close crop of sky from one of my shots with Fujifilm 400.
You can see the grain but it's much softer and not as contrasty. I'm using super technical terms because I only just started shooting film.