Reason for rejects

All of your assets should have been refused. Those that got accepted, got accepted by error and the first buyer will complain about them. There is no need for an extensive critique here:

• they all contain excessive noise
• none of them is focussed
• Suzuki is a trade name that needs to be removed.
• you need to clean your slides before scanning and check after the scan for any leftovers.

After several months of digital photography with my then new Canon EOS 20D with that cheap kit lens, I went back to sort out some of my slides and film pictures. I was astonished how fast I got used to the clear digital images, and I stopped pixel peeping my digital shots. None of my film pictures were sharp enough, even that I used a great lens at the time. Then later, with my 5DMark IV and my prime lenses, I had again a new view into sharp pictures.

Unfortunately, old film pictures are rarely meeting the quality requirements for stock. And that is independent of your photographic talent. The most prestigious photographers of the time would not get one asset approved, by stock quality terms. Well, that was true until shortly, before Adobe added numerous inexperienced moderators.

You answered your own question. Excessive grain. Lack of clarity with seals. Film stills usually won't get past the moderators. I'm surprised the boat sunset especially was accepted, since the horizon line is tilted.

I'm actually surprised that any of these wrestlers accepted. It's rare for scanned film photos to meet current quality standards. All are grainy, softly focused, have artifacts and some have leaning horizons.