This is what theu are actually saying (at least the articulate among the trans community) :

"Seeing a lot about Caitlyn Jenner today. And I am so happy for her, I truly am. And I think it's wonderful that the media are covering her transition and hopefully reaching and fostering understanding in people who would otherwise not be clued in to trans issues. I think it's wonderful for someone who was famous for their achievements as their birth-assigned gender to be able to publicly transition I can't imagine how hard that all must have been.

My issue with the whole thing is that she has money, her transition has been swift since her public coming out, there is no way that she can now be read as anything other than a woman, when the reality for most trans people is not that easy.
It takes years, and money, to get even hormonal treatment never mind surgeries should they want them. There are the risks involved with chest binding, there's the struggle of buying clothes when you're read as your assigned gender, and on and on. Misgendering can lead to physical attacks, verbal abuse, being refused housing, jobs, even familial support.
I'm glad for Caitlyn's sake that her transition has been, from what I can tell, smooth. But to hold her up as representative of the trans experience is idealistic at best and damaging to a lot of trans people at worst."