Yeah, despite the numbering they absolutely are prequels. Imagine you were born under a rock and started watching Star Wars from Episode 1. You’d think the Imperial March was just a motif for Anakin doing bad stuff. The clonetroopers and Venators would stir absolutely zero familiar imagery in your mind. Jango Fett’s son would seem like a strange thing to focus on. Anakin being renamed to “Darth Vader” would probably conjure a laugh because it’s a nonsense word and you do not yet associate it with a big scary cyborg man. “Luke” and “Leia” would hold no meaning for you, and neither would Owen and Beru watching a twin sunset. etc.

I also don’t think the Original Trilogy works very well as a sequel to the prequel trilogy, if you know what I mean. You might have questions like - why does Luke only have to train for a few weeks, or a year at the absolute most, to become a Jedi? Why doesn’t Obi-Wan mention that Luke and Leia are related so they don’t keep kissing one another? How come no one can jump anymore, and fight like geriatrics? What happened to Sidious’ lightsaber skills? Why does Vader never mention Padme? How on Earth does Leia remember a mother who died thirty seconds after she was born? Why does Obi-Wan continue to wear Jedi robes on Tatooine? Why doesn’t it occur to Obi-Wan and Yoda that some of the ten thousand other Jedi might have survived? I mean, all of these little nitpicks exist anyway, but watching in release order makes them less apparent unless you’re being deliberately anal.