I dont necessarily think its nostalgia thats the reason behind Super’s relative success. Its really just more the same of what Z gave us, and people are happy with that (why wouldnt they be?). Its not like any of the issues Super suffers from weren’t present in the original. There are no reasons for the majority of fans not to like it. DBs main attraction is its crazy fights, powerups, quirky villains and cast, all of which are present in super.
DB is an absolute classic and was incredible in it’s time, but the series was never any more than average in regards to writing. Z literally repeats the exact plot progression every single arc. If anything, Super has done a better job than it in that regard. DB just hit all the right notes it had to to resonate with readers, and Super seems to be following in its footsteps. Its pretty acceptable as a sequel in my eyes and much much better than what I was expecting (which was just a copout cashgrap like good mate Boruto has become).
I do however, think they should have just made all the arcs as movies though. 1 for the Universe 6 arc, 1 for Black Goku, 2 for the current arc. Considering Battle of Gods and Golden freeza were 2 of the 30 best grossing anime movies ever, and following the trend, any future movies probably would have done even better, I seriously wonder if making a tv broadcasted series was be more profitable. Though I guess it is or they wouldnt have done it.