Shi Feiyang's last refinement of the Nine Demons and Nine Swords could not break the Liangyi Dust Formation but merely provided him the power to retaliate when facing supreme experts like three monks, two nuns, and Yan Yingmu. This ensured he was not limited to just taking blows or fleeing but could speak to them on relatively equal footing.
However, even so, he was still helpless against the Liangyi Dust Formation, and reaching the fully-fledged formation of Emei Mountain was definitely out of the question. Therefore, for whatever reason, he would never venture to Emei Mountain, nor could he carelessly let his opponents trap him within the movable formation formed by the combined forces of three immortals and two elders.
If he could refine the ultimate version of the Heavenly Secret Demon Great Technique, combined with his insights into the Liangyi Dust Formation, he might have a fighting chance should his enemies deploy such an Array in the future.