At the time, there was a general agreement that the English wordstock wasn't broad enough to compose elegant poetry because poets needed words that could fit the specific meter of the poem.
文学百科 The Literature Book (Big Ideas Simply Explained)
After, 1668. Jean de La Fontaine adapts his collection of fables from classical sources, including Aesop and Phaedrus, stretching the metrical verse of the time.
Therefore, Chaucer is considered as a great master of the English language, for he greatly increased the prestige of English as a literary language and extended the range of its poetic vocabulary and meters.
Recognized by his contemporaries as the foremost poet of his time, Spenser was not only a master of meter and language but a profound moral poet as well.
The metaphysical poets wrote of God and of theology, of the court and of the church, of love and of nature with a high regard for form and the more intricate subtleties of meter and rhyme.
That suggests that he didn't have time to compose highly structured passages using iambic pentameter or some other meter, or passages using rhyming verse.