Sentence:  However, he had not yet at that time fully displayed the principle of expression through intonation, the amazing ability to construct a line of verse in accordance with the most ready-to-hand, most colloquial speech - a characteristic which makes some critics group him with the <WSD>intimist</WSD> poets who write of the most complicated inner experiences, ostensibly inaccessible to the ordinary reader of today, and which makes others see him, no less mistakenly, as far too closely continuing the Futurists' methods of fashioning language. 
Meaning of the word marked with <WSD> tags:  Introspective; concerned with inner life and psychological experiences.