(Edit: To be clear, I make this point or ask this question out of curiosity. I'm not trying to assert or establish any standards or ethical positions. It's just something I've never explored before, and I'd like to know a bit more.)
What I'm about to write may be wrong, it may be pointless, it may be both. It's just an idle though I've had.
I've read a few articles in a few different places making the case that viewing breasts as sexually alluring is a construct of modern society and not intrinsic to the human race. For example, Men Aren't Hard Wired to Find Breasts Attractive
I think accepting GLBTQ+ in general means rejecting conventional views on sex, gender, and sexuality and that would include moving away from a focus on breasts in sexual terms. But my very limited understanding of trans people is that most people transitioning to female consider the presence of breasts important and most people transitioning to male consider their absence important.
I'm not criticizing that. I just find it fascinating that the presence of breasts seems to be important to the female identity in the trans community even as - ideally - we as a society should move away from making a fetish of them. I guess it means the presence of breasts are important to women regardless of sex and sexual attraction? I'm a cis+het guy, I have trouble separating "breasts are feminine" and "breasts are sexy". I guess I've got to work on that.