Why did the neoterici reject the grand style of Ennius’s poetry?

The neoterici (or neoteroi) rejected the grand style of the Ennian tradition because they sought to break away from the didactic and patriotic conventions that dominated early Latin poetry.1

They specifically criticized the Ennian style for its:
* Excessive stylistic devices: They deplored the heavy use of alliteration and onomatopoeia.1
* Technical structure: They rejected the "ponderous metres" that characterized traditional epics and didactic works.1

In contrast to the grand, nationalistic epics of poets like Ennius, the neoterici favored a more refined and sophisticated aesthetic. Influenced by Alexandrian Greek models, they cultivated "art for art’s sake," focusing on meticulously crafted, shorter forms such as epyllia (brief epics), lyrics, epigrams, and elegies. Their work emphasized self-expression and a lighter, more elegant approach to literature, which stood in direct opposition to the expansive, historical narratives of the earlier Roman tradition.1