[notacoward]

First, network effects. Amazon was able to grow because there wasn't already an Amazon that they'd have to pry users (and sellers) away from. No replacement will have that luxury. Even harder to wean people off Google search, let alone Chrome, let alone Android. In social media, many people are unwilling to leave all their friends (and family) behind to go somewhere and be a stranger again.

Second, funding models. Because of that network effect, nobody will dump the ungodly amounts of cash on an Amazon or Google or Facebook replacement that they dumped on the originals. They can't grow, so they can't compete, so they can't grow, etc.

Third: regulatory capture. Meta is the clearest example of this, secretly funding PACs and lobbyists to get regulation that they are well able to comply with but no smaller competitor possibly could. It's an effective moat.

"If it was done once it can be done again" is just wishful thinking. It's not generally true, and especially not in internet-facing tech. The soil is already depleted, or even poisoned. Reining in the incumbents is a prerequisite to any alternatives getting on their feet.