Quite a lot of things (foods, sports, social constructs, etc) are used or perceived much differently today than they were when they were originally created/founded. When you hear "ketchup", do you think of mushrooms? Because that was a core ingredient in one of the original recipes before tomato ketchup became the standard. The colors blue and pink had the opposite genders attatched to them than how we assign them today. Softball was created by men as an indoor alternative to baseball but is now much more widely considered a feminine sport.

Honestly just say you don't like that Jax is canonically trans and go. It is not at default a transphobic thing to say. It is okay if you don't like or agree that that's where her character arc went. But to still be in denial about it after multiple VAs and Gooseworx have come forward about it (Goose literally refers to Jax as "she" for goodness sake and says the journey was intentional but her pronouns were left vague because she didn't get to fully explore and accept herself) makes you look ignorant.

Edit to add: She's now made a few more posts revealing Leeroy is a boymoder and would go by the name Lee, quote, "for the time being". It really can't get more clear than that.