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.
Have you moved on from Drupal? Let us know in the comments! What are you using instead?
Edit: The chart data has been updated as of December 2018.