Gameplay changes leading to spinoffs can allow both styles to be run parallel, rather than disappointing fans who prefer one of the other when the next game in a series isn't the style they're into. As an example, suppose someone significantly prefers 2d games to 3d games. An announcement of "the next Metroid game" would hold more weight for them because they can be reasonably sure it will be a 2d game (as distinct from announcing "the next Metroid Prime game"). The question then becomes whether Let's Go's mass simplification is sufficient for it to be separate. Because I love complexity, my answer to that is yes.