I remember the RSS times. But let's be honest. Even then it was only tech enthusiasts using an RSS reader. Probably the same people now experimenting with the Fediverse.
Do I trust Meta regarding federation? No. But I'm thinking it's an afterthought for them. The Fediverse isn't a threat to them at all, just like RSS never was.
I totally understand that some instances have strong opinions about this and self-isolate to a degree. And that will cement what Mastodon is: a set of small for-purpose communities.
It will not compete with the scale of Big Tech and maybe it shouldn't. Mastodon is to stay in their marginal role, a niche network. For sure exactly those strong-willed instances will agree to that.
I'm fine with that as well. I'm just pointing out that an anti-growth mindset produces a small network.