The reasons why this person's calligraphy cannot be learned are that the calligraphy style lacks variety, is considered too "vulgar", and deviates from the calligraphy tradition of the ancients in some aspects.
1. Tian Yingzhang’s calligraphy style is considered by some to lack of change. Tian Yingzhang's fonts appear to be relatively single in some cases. Whether it is the shape, thickness or posture of the strokes, they all appear to be relatively consistent and lack sufficient changes. This lack of change in style is considered to limit learners' space for calligraphy development, and may even cause learners to form a fixed mindset and their writing to become rigid.
2. Tian Yingzhang’s calligraphy was criticized by some calligraphy teachers as “vulgar”. The calligraphy teacher believes that Tian Yingzhang's calligraphy pursues too much superficial beauty and lacks the artistic connotation and lyrical attributes that calligraphy should have. Real calligraphy should be expressive and not as rigid as an operator. Therefore, calligraphy teachers worry that learning Tian Yingzhang's calligraphy may lead learners to deviate from the true connotation of calligraphy.
3. Tian Yingzhang’s calligraphy is considered to deviate from the ancient calligraphy tradition in some aspects. Tian Yingzhang's brushwork has been criticized as being too simplistic and not inheriting the calligraphy spirit of the ancients well. This can make it difficult for learners when trying to learn any calligraphy style because the learner's "muscle memory" has adapted to Tian Yingzhang's calligraphy style.