It's not quite as bad as video game adaptions usually are, but VNs just in general struggle in adapting to anime. I think it mostly comes down to the fact that Anime can tell a story quickly and with a focus on the plot while a VN tells a story slowly and with a focus on the characters.

A two-minute scene in an anime could be a thirty-minute scene in a VN depending on how much that VN focuses on the thoughts of a character or exposition.

At the end of the day, studios are aware and wary of this and know that there is an inherent difficulty that isn't really there with manga or even LNs.