It's only a Twitter alternative if people I care about will read what I write, or I can read what people I care about write.

Until most of the publishers are dual-publishing (or migrated), or most of the readers are dual-reading (or migrating), it's not an alternative.

GAB is a niche Twitter alternative.

the main alternative is facebook if the use case is media comsumption. if the use case is following experts in your industry its just feedly or rss

Not even close.

What's that?