Lesbian romance would tank sales as hard as heterosexual romance.
Yuri fans despise lesbianism almost as much as yuri haters; they only follow an anime / manga if it has females interacting with each other because it allows them to project and imagine things without being "real".
1. Hibike Euphonium is considered the definitive yuri show
2. NanoFate is considered the definitive yuri couple even when they've never kissed, declared each other's love in no ambiguous terms or have sex on screen for as long as the franchise has existed (15 years!)
3. The threads about shows featuring female characters interacting regularly (SSSS Grindman, Zombieland Saga) are full to the brim with Yuri fans even when the shows themselves have no yuri content at all
4. The threads for shows depicting actual lesbians (Bloom into You!, Citrus, Sakura Trick) are either ghost towns or dens of shitposting and those anime / manga are considered "absolute garbage"