Not sure, if this is truly the case. For example, on reddit I was mostly subbed to queer or queer friendly communities. And in my feed only appeared these communities. In how far would this be different in decentralized and federated communities? And apart from that, we all still have to constantly live people being bigoted over here, as everyone has it all internalized. E.g. I'm white and come from a academic context, so I have to make a conscious effort to keep this in mind while participating here. And if someone else writes in any of the non queer-related communities, they are statistically speaking neurotypical and cishet, so I easily feel (and am) excluded in some way.
My point is, it certainly helps to have decentralized spaces, but in order to abolish structural discrimination etc we still have to be conscious about it and make an effort.
Regarding your last sentence, I would guess that generally social media are more attractive to queer or otherwise marginalized people as they can meet likeminded people. See any of the leading social media.