I strongly disagree with this assertion that the popularity of Echoes is simply people "falling for fancy marketing", I made this post before but there are three reasons I see why they're are a lot more popular this time around than clones were of the past:
1: People are much more knowledgeable about the reality of the clone development nowadays, so you have few people still legitimately thinking the clones are "taking a slot" from a unique newcomer, which was the main reason most people disliked clones.
2: Echoes are being revealed upfront for what they are, unlike in Smash 4 and Melee where all the clones, besides Lucina, were kept secret until release and were presented as like any other character. The other big component of the backlash against clones in prior games were people getting really disappointed when they were expecting these popular characters with a wholly new moveset kept hidden for a surprise, for it to then turn out to be some clones, leading to significant disappointment and a terrible initial impression. Even characters with partial minimal cloning were subject to this, as the whole reason Wolf had a significant hatedom among the casual fanbase in Brawl was because they were expecting Ridley or Mega Man or some other big character with a whole new moveset for the final secret character and instead got what was "JUST ANOTHER FOX CLONE?!" in their view. This is also one of the main reasons why Dark Pit is a lot more hated than Lucina, as he was seen as a tremendous letdown for what people expected, while Lucina was revealed upfront as a clone and shared her reveal with a fully unique newcomer.
3: Most fans of the popular Echo candidates realize this is the only realistic chance their favored character has of getting into Smash in a playable capacity, and thus will gladly take it over getting nothing at all, while even for those with a more realistic chance to get in as their own character like Dixie, many fans will still take this easy ticket in rather than risk not having them in.