Pretty much every design system out there disagrees with you. Material (Google's design system) uses 10 shades, Fluent (Microsoft's) uses 8, Lightning (Salesforce's) uses 12. Even the most basic terminals in use support 2 shades of EACH color.
While 2 or 3 colors are fine for a simple blog, any app that has more functionality than just reading can benefit from a wide range of semantic colors. A dangerous action should be red, a graph trending upwards should be green (or red in East Asian markets), a warning should be yellow. These colors help convey meaning to the actions that are present, and the usefulness of a wide spectrum should not be discounted.
While 2 or 3 colors are fine for a simple blog, any app that has more functionality than just reading can benefit from a wide range of semantic colors. A dangerous action should be red, a graph trending upwards should be green (or red in East Asian markets), a warning should be yellow. These colors help convey meaning to the actions that are present, and the usefulness of a wide spectrum should not be discounted.