We're just past the second anniversary of 8.0.0. To see how D8 is doing compared to prior releases, we put together the chart above, based on Drupal's usage stats page.
For versions 5.x, 6.x, and 7.x, each new release brought dramatically accelerated growth.
Comparatively, D8 has dropped off a cliff. Adoption is far below that of D7, and even behind D6.