Truth Social has a ceiling
Conservatives have made no secret of their frustrations with Facebook and Twitter, and many have flocked to alternative platforms like Gab with looser moderation riles. But these free speech oriented platforms ultimately will not compete with Big Tech because they have a built-in ceiling on their user base. Donald Trump's new platform, Truth Social, will hit the same ceiling.
Now, to be clear: I am very glad Gab exists. I have been on Gab for nearly 4 years, having joined in January 2018. While there are unsavory characters there, I have dealt with more unsavory characters on Facebook and Twitter than I have on Gab. I also do not deal with nearly as much spam on Gab as I do on Facebook. There is a working block button on Gab and a number of interesting people to follow. Gab is definitely a very valuable free speech platform.
With that said, these alternative platforms do have inherent weaknesses. Facebook was originally not a political platform. It was a social network, mostly for college students. I originally joined Facebook way back in 2006, when MySpace was the dominant social network. There were political things on there, but mostly it was non-political. Because membership was so limited, Pages were not a big part of it. Facebook, then, was marketed to as wide of an audience as possible once it opened up.
This is not the case with Gab or Parler, and will not be the case for Truth Social, because of how they are marketed - as a way for conservatives to speak freely and without censorship. Because they are seen as conservative platforms, progressives are less likely to get on board. That is a large audience that alt-tech is struggling to bring on board, and without a wider audience neither will be a true threat to Big Tech.
Plus, as I said earlier, there is a wider set of interests on Big Tech. While many people join Facebook and Twitter and never post anything political, Gab and Parler (and soon, Truth Social) are explicitly marketed as "free speech" political platforms. So if you want to follow news about movies, sports, video games, cooking, exercise or music, Big Tech is a much more natural destination than the conservative platforms. "Alt Tech" will need to find a way to expand the interests on their platform by attracting non-political viewers.
It may be possible for an alternative free speech oriented social network to truly compete with Facebook and Twitter, but they will need to push for a much wider user base and more interests. And like it or not, they will need to attract "influencers" to the platform, in many more categories than political thought. And remember, it was only 15 years ago that Facebook was very small and MySpace dominated. These things can change very quickly. Big Tech is not destined to eternal dominance.