People are very fond of pointing to I have numbers! Stats on LGBT Young Adult Books Published in the U.S., which is a fine piece of work. However, it doesn't have a crucial bit of information: how many LGBT YA books were submitted? Is the acceptance rate for LGBT YA higher or lower than it is for general YA?
One fact stays clear: Science Fiction and Fantasy YA novels with Major LGBTQ characters exist. If you want publishers to publish more, buy more. It took the success of the ipad to convince the computer industry to sell tablets. That's just how capitalism works.