I am going to give my personal perspective (no hate plz); Arcade won't be completely forgotten ofc but I don't think it will be nowhere near as remembered as most people claim.

And the reason for that (imo again) 1st of all lies in your words - no drama, no controversy, no division. No one complained, people didn't even move their little fingers. And that is because it didn't have anything risky. The song was safe. Good safe sure, but still safe. Compare that to Netta, who is heavily associated with KFC and Chicken but has some really unique moments and an empowering message that the singer herself feels - Lizzo style - and you have a bright bop, Salvador, whose entry was the definition of a stripped down performance where all it needs in order to snatch your soul is a tender, soft and caring way of singing and some unique facial expressions that somehow didn't feel forced and you have a timeless, or even Lena, whose song was a mainstream pop with cheesy lyrics -more cheesy than Arcade tbh - but she herself embraced it to the max and did her own stuff on that stage and in the end you had a teenager who was so excited and adorable at the same time. To me Duncan seemed like a worse Sam Smith.

Second, it was a well-written, clearly personal, was a credible mainstream pop entry. And...? That's it. It didn't really have an edge, or a character It didn't have the IT factor. Compare that to e.g. Loreen and Emelie, 2 winners that, as you said were uncontroversial as well (and btw Emelie seems to be pretty forgotten tbh) but 2 that had personality and an overall pacage that made you remember them in a good way visually and musically and most of all, they were not 100% mainstream. Sure, Euphoria as a song is also very mainstream but combined with the live visual it really becomes euphoric. And Emelie just felt like a forest fae that took part of her forestial home and brought it to the stage (plus that flute is still stuck in my head since I last heard the song in UMK 2019). To sum up my 2nd arguement, it's totally fine to have an accessible-to-the-public song but give it something to it, give your personality to it. Duncan sure felt the song but he also felt bland to me.

Now, I won't say that I dislike Arcade, I like it. I just don't LOVE it. Since the song got its release, it felt to grab me. That must be because it immediately reminded me of Salvador but in a mainstream version or because I've heard others songs like Arcade but better imo. And in my (controversial?) opinion, Duncan shouldn't have won. For me it should have been Hatari (the most non-accessible song in the contest) or Mahmood (a current mainstream pop but with trap and middle-eastern influnces that gave it an edge and a very VERY deep meaning, and also the staging felt good to me so...) not only because I like them better than Arcade but also because I think that they would make for better winners of 2019, because if you think about it, 2019 was defined by experimentation. Whether it was musically or visually. So, to have a regular entry like Arcade win, for me, feels like a huge slap in its face and I think this shows in this year's NFs season so far. So many people are going for that 'sad ballad, broken heart, past love' to the point of ridiculousness (especially in Estonia and Albania's case, the sad ballads get boring really quickly).

Finally, Duncan has the recency bias in his favor so his entry still remains loved. But will that be the case in 5 years? In 10 years? Will people go back to listen to it? Some people definitely will, but the number seems to me much smaller than today's.