That is all completely valid
Speaking so broadly, obviously there are many outliers in both eras. On the matter of imitation vs. homage, I think I usually assume most artists that are doing retro-themed stuff are doing it with a certain level of wink and nudge. Take everyone's favorite The Weeknd for an easy example. The After Hours album was all synthpop style, and while I'm sure many people would say he's just ripping off old stuff and dismiss it because of that... the reality is that he's doing a bit, and it's not like he's hiding it. He's not at all trying to pass the style off as his own. Whether anyone enjoys it or not is obviously up to them, but in a case like that, I don't think much should be made about the whole imitation aspect of it.