Why Chaucer is known as the earliest of the ‘Great Moderns’?

The death of Chaucer came too soon after The Century Tales. The tradition of Chaucer’s masterpiece had no time to take firm root in the soil and the result was that literature went on as if The Tales had never been written.

His imitators regarded him as a wise philosopher and failed to appreciate his wit, his humor, realism, and his technical skill. They went to his earlier works for inspiration rather than to his masterpiece. The result was that poetry instead of advancing along the line laid down by Chaucer, returned to the medieval groves. Instead of progression there is retrogression.