Originally T was added for transsexual homosexuals. And LGBT was still ONLY about sexuality. Now T was hijacked by "transgenders" who are not even transsexuals with "born in wrong body" but some people called "transgenders" (previously transgender and transsexual were synonims, as gender was equal to sex, but not anymore) with "I feel like other sex" or "being other sex is my kink", and QIAANB+ part added was not about sexuality either. Almost everything that is after LGB nowaydas is about either sexual kinks or "how you feel yourself" or "what stereotype you will like to follow", not about sexuality at all. Plus if LGB is mostly about acceptance and "we are normal, just like everyone else, let us live. Being homosexual is same as being with brown or white hair, nothing special", the TQ+ is about "we are different, we need more rights than other people, make sure to remember that we are different and use special pronounses, change the world". And in general TQ+ has a lot more in common with movements like Feminism or Men Rights Activism.

And this is main issue with TQ+ under umbrella term - they want absolutely different things than we (LGB) are, they have absolutely different problems than we have, and even whole core reason of those problems is different. If Lesbians, Gays and Bisexuals have something in common - romantic and/or sexual attraction to same sex people, if all LGB people have same reason for being oppressed and it is shown in same way to all of them, then TQ+ have nothing in common both with LGB part and even within themselves.