Your not the first I've heard with that opinion, and it really does illustrate the different ways we see Star Wars. For me, and it seems others, we are not viewing them as Prequels, Original Trilogy, Sequel Trilogy...but as one whole. yes they all have different "feels" about them because of not only the era's they take place in but also when they were filmed. ANH had a lot against it when it came to the duel. Lucas didn't really have the full story solid yet, Prowse had no interest in learning choreography, Sir Alec was a 62 year old man with no training, the on set lightsabers were very fragile so they could only really tap them and they had to rotoscope the blades over each film cell. All this lead to a very slow paced duel that, tbh, didn't have a lot of heart to it. For many though this was their first taste of Jedi vs Sith...be it you saw it in 77 or were younger and saw it.
While it may work within the OT, in the larger it doesn't. There is no in universe reason for them to be that sluggish. This fight shows two aged and more experienced warriors who abandoned the over flashy flourishes for the most part and are focused on ending the fight that has brewed for 20 years. Also the physical manifestation of Vader's rage in his movements. For me, it works much better than the original duel. Doesn't mean I think it should be edited in to all copies of ANH nor is it without its flaws, mostly due to the fact its fan made and not big budget.
When taken as a re-imagination and put into the larger context of the story as a whole, it does work. However, I've always viewed each SW film as a standalone first, and a piece of a larger story second (one of my biggest problems with TLJ). Because of that, it just doesn't seem like it belongs. Also, I've always got the feeling while watching the original scene that Obi-Wan is doing more than fighting Darth Vader, I always felt like he was buying time for Luke & Co. He knew that he was not going to make it off the Death Star, so he provided the much needed time for the others to do so. With that in mind, the other, slower, more specific fight makes more sense to me. Had they wanted/needed too I definitely think it could have looked like this, but I don't feel like that was needed. Also, though fighting and choreography is super awesome to me (I'd love to get into stunts), Sir Alec's acting was what sold me here. I am primarily an actor, and though at the time of my first watching I didn't realize this, the acting obviously had an impact on me. So while the duel itself wasn't "spectacular" the story and character of Obi-Wan vs. Darth Vader (who even if we hadn't watched the Prequels yet knew that they had a long, sad history) made it that much richer. It is a great scene no matter which version you like, and I'm not saying that anyone is wrong for liking one over the other. We all have our opinions, and we all watch the movies differently. Like Knox has said many many times, movies are subjective. That is the beauty of these films. We can discuss them and explain our opinions, and (most the time) people don't have a problem if you don't share their opinion.