You assume this is the only way, and it is true if you take as an axiom that everybody is equal and has equal right to be represented, to access the platforms and to participate in a public discussion. This is not however what leftist culture warriors think, and unfortunately for people who disagree with them, they now are controlling most of the Big Tech platforms and most of the corporate press. As the result, the values which they disagree with are and going to be suppressed, and they are absolutely OK with it - moreover, they consider it vital and necessary.
They do not want to learn to engage anybody they disagree with, and as long as they control most of the platforms, along with the academia, the education sector, the entertainment sector, serious part of the government institutions and significant part of the corporate boards - there is no reason for them to engage anyone, as soon as they can just suppress and deplatform whoever they like. Might makes right, at least for them.
Of course, there's no technology on Earth - at least not yet - to make dissenting voices completely silent. But that's not the point. The point is to make them orders of magnitude weaker, so they would not be able to influence anything. You can talk to your friends in your kitchen, if you want, while your opponents will have an access to billions strong audience. You can set up your puny webserver (provided your ISP and your DNS provider do not deplatform you, and your bank does not deny you access to payment systems) - and you'll be competing with the combined powers of Amazon, Google, Facebook, Twitter, Apple and such. Do you think they would feel compelled to "engage" you, to evolve and change their ways to account for your existence - or would they just crush you like a tiny insect, and not even notice it?