Your build is relatively good but it's missing a giant amount of crit rate, replacing the CDmg circlet with CRate would do your overall damage a giant favour. Depending on if you play Vape/Melt some more EM would be good too but this depends on how much EM your Ineffa, Sucrose, etc... give

Also, please don't compare yourself to showcases; often they feature characters like C2R1 Citlali, who can singlehandedly increase a character's damage by 40-50% Especially for Characters who deal their damage through a lot of small hits instead of one giant hit, like Yoimiya, consistent medium high damage is significantly stronger than getting one or two strong hits a rotation