It's definitely one of DC's many attempts to capitalize on the popularity on Superman 1978. But IMHO there is a difference between paying homage to a specific period of Superman history and this project.
A comic book like this:
https://en.wikipedia.org/wiki/Superm..._of_the_Worlds is what people call a pastiche. It is made in the style of a pre-existing work (in this case, Golden Age Superman and Wellsian sci-fi). But it is entirely about the style (aesthetics, dialogues, etc.). This is what I consider a version of a character from a specific continuity.
IMHO Superman '78 is on a different level because there isn't anything particularly remarkable in terms of style - it's just the classic, generic Superman setup, Clark Kent as a shy, mild-mannered reporter, Superman punching Brainiac etc. It's not even made with a specific 1970s sensibility, since the story is basically inspired by relatively recent works (and the original Superman III, as Donner - I think it was him - envisioned it, was completely different). It's more or less entirely about the characters looking like the actors. It reminds me of a page in Alan Moore's The Tempest (the final volume in the League of Extraordinary Gentlemen saga) in which superheroes are depicted as decrepit icons which corporations refuse to let die because they want to continue exploiting them. I don't think that stuff like Superman '78 is what Alan Moore had in mind when he wrote that page, but it's definitely the first thing which comes to my mind.
I don't want to convince anyone that I am right, it's just my opinion. I guess that it is quite normal in the world of pop culture to deal with this stuff in terms of estates and likeness instead of real people who had a real (and unfortunately sometimes tragic) life. I just can't help finding it weird.