Rosemi is basically the Gohan of Nijisanji EN.

Just think about it: The former wave had livers like Pomu Goku: always consistent, basically the strongest even if others shine brighter for some time and Ewiwa Vegeta: basically on par with Pomu, even if her streams are not as consistent. Relateable and a fan favourite. She was seen as the next big thing and was very powerful for some time - as if she was a better Pomu. And then it was like her arc ended which left her being a shadow of her former self. The next wave introduced livers like Millie Goten: pretty similar to Goku, but smaller. Still great. and Enna Trunks: a fan favourite, smol, very powerful and even moreso fused to Millie, she declined while those new ones shone... and now she's not much more than a distant memory of a better time.