Meta doesn't bother me too much.
I'm more concerned with YouTube owning all of social video. Movies are on a dozen streamers. Social stuff is on Instagram, TikTok, Reddit, and X. But video essays, independent animation, educational content, cultural critiques, music, video podcasts, trailers, gameplay, research, news - anything long form, serious, interesting - it's all trapped on YouTube as the only distribution platform. And they'll keep getting bigger with no possible alternative due to network effects.
I'm even more concerned with Amazon being a conglomerate [1] that is in online sales, hyperscaler infrastructure, consumer hardware, home automation systems, grocery stores, medicine, primary care, and movie production. And that they can leverage these synergies in grossly unfair ways.
I'm most concerned that the Apple / Google duopoly in mobile, web, and search has entrenched these two players across the vast majority of online transactions, interactions, and computational device usages. They collect margin on everything. They own your devices, they own search, they own the web, they own the apps, they have to be paid off to rank your business, have to be paid off to collect money, they regulate what you can do with your apps and websites, etc. etc. You jump through their hoops. This is their internet.
[1] Especially given the fact that Amazon can subsidize their efforts in these areas from profits in other business units and out-compete viable businesses in those markets. They can offer goods for free with an existing subscription and advertise far and wide across their retail website, plastered on their packaging, and emblazoned on the side of their delivery vehicles. Lord of the Rings got an 80 million dollar advertising package for free, whereas Bong Joon Ho's far more deserving film got next to nothing.