This is an organic development from a global community. Neither I nor anyone else speak for the community, definitions will not be universally accepted and they will change over time. Being said, “queer” was initially a term of exclusion. It meant anything other than “normal” (where normal was defined by the oppressors as cisgendered, heterosexual, and heteroromantic). I seet was, at the time, intended in a negative way. When I use it now, I keep the denotation and invert the connotation. Why yes, I am absolutely not cisgendered, heterosexual and heteroromantic. I’m something other than those three things in combination and I’m owning it. I like queer because it automatically expands to include new ways of being as they’re discovered. When I was a kid I knew I wasn’t straight because women turned me on and men turned me on. So i went with "bi”. Now I’m in a relationship with a trans person. That kinda means “bi” doesn’t fit, or at least my understanding of it at the time didn’t. I could’ve moved to pansexual but, frankly, I didn’t feel like it and a lot of people use bi to mean “hetero and not-hetero” rather than “man or woman” or “gay or straight”. So that’s a second time my sexuality, or my understanding of it, has shifted. Then I discovered the concept of demisexuality. Understanding myself better is, of course, a big plus but that means I’m now a straightbisexual because I like men and women anyone potentially regardless of gender but I’m also demi. It gets really complex, so I just say “queer” and then am willing to address any confusion that arises from that as well.
As far as leaving letters out of the LGBTOMFGLMAOBBQ+ acronym goes, I’ve not run into anyone who took that as an intentional slight other than with the Aunt Toms in the “drop the T” movement that wants to exclude gender queer people from the queer movement. Unless you’re intentionally trying to divide the community by excluding people, the myriad subgenres of queer including those that haven’t been discovered or popularized yet are what the q and the plus are for.