You’re not paranoid, and it does matter. Distributed systems definitely struggle to stay distributed. Git is a great example, as are most cryptocurrencies, which despite being distributed by design, generally come to rely on centralised wallets and trading platforms.

The web itself seems to be be becoming more centralised- more people spend more time on fewer websites. Websites are increasingly being hosted on a tiny number of mega cloud services, rather than millions of independent server rooms.

Centralisation is a real concern.