Remember when, every day, we gush over the indiana jones adventure miniland that never was? The mine train, the railroad, jungle cruise, all sharing a large ride/show building with the ride we eventually got? 30 years later, they dedicate an entire land to another lucasfilm IP and everyone is upset about it. D***ed if they do, d***ed if they don't. If we got one star wars ride in tomorrowland or an overlay, people would have been livid. They did everything they could to separate the lands and to design Galaxy's edge to actually enhance the back splash of the rivers of america with new forests and new mountains. They have a style to them that is quite alien but overall, they are not in a cartoony art style like splash that doesn't fit the realism of frontierland. Every other attraction has an iconic facade and gets a free pass, but somehow star wars should be invisible? Nope.
Discovery bay was cool, but whereas the core disneyland lands were pure ideas and themes in strict isolation, discovery bay was an assemblage of frontierland, tomorrowland, and new orleans square. It was vague. I think it would be delightful at DCA but is redundant at disneyland. As much as SW:GE is a departure from the purity of the disneyland core lands, at least it doesn't try to compete with them thematically and muddy their clarity. It is an indiana jones adventure departure from Adventureland, on steroids, and it doesn't hurt the rest of disneyland. Not putting it in tomorrowland means that even though we are about to have a massive sci-fi presence at disneyland resort, with star wars and then marvel, each with grimey and often dystopian manifestation themes, tomorrowland has been left alone so that we can hope for a pure, clean, optimistic vision of tomorrowland in the future, rather than one littered with grafitti, aliens, dystopia, and IP.