I wonder if much of the perceived ‘lazy’ design of this set stems from Lego’s own decision to primarially brand and market the set based on its similarity to the original Eldorado Fortress?
Imagine if – rather than promoting the set as a faithful remake – Lego had instead chosen to place the current main alternate build on the front of the box as an original creation (complete with its own unique name/identity - e.g. Eldorado Redoubt/Landing/Trade Post?) and placed Eldorado Fortress on the back of the box as an alternative build/Easter egg? In other words, the same approach as Pirates of Barracuda Bay.
While this switch would address none of the substantive design critiques (e.g. black vs brown docks, 'gappy' parapet walls, simplistic palm trees, lack of art/lore in the instruction manuals etc), the psychological effect in terms of perceived total creativity/innovation would, I believe, be reasonably profound.
There are some hints that Lego may have considered taking this approach – for example the lifestyle video on Lego.com focuses almost exclusively on the alt build.
Ultimately, they clearly decided that appealing directly to the traditionalism/nostalgia of the original Eldorado Fortress was the safer choice.