A big tech breakup needn't be anti-capitalist. In fact, it might be the most pro-capitalist move.
If you're an entrepreneur or VC, you want big tech broken up because they can put serious price pressure on your exit.
Trillion dollar companies can easily spin up a team to copy you, with no incentive to stay alive. They can threaten you with all kinds of leverage - access to customers, patents, legislators. They can give you an ultimatum to sell for cheap, go to your competitor, etc.
Their scale and reach is additional unexpected gravity on your delta V.
Capitalism is supposed to be hard. It isn't supposed to support invasive species that can graze anywhere they please and kill ecosystems of diversity and innovation. These mega conglomerates can just throw themselves into markets using unrelated business unit profit and suffocate real companies.
Breaking up Google and Amazon would be good for everyone, perhaps even shareholders and ICs at those companies themselves if value is unlocked. Let alone all of the other companies and entrepreneurs in the market.
I think it depends on which kind of entrepreneur you're aiming to be. VC breakups are amazing if your goal is to box in and become a market competitor. But as of the last decade or so there's been plenty of "incubators" to take into account. startups whose goal is instead to be sold off to some major company and get their payday that way. Those kinds of models would deteriorate, and are likely what want to prop Big Tech up.
I do hope we have more genuine competitors fighting out there for breakupps. But it's hard to say these days.