Comment by tsimionescu

It very much is.

Even the web suffers from problems of trust to some extent, with the PKI being a huge vulnerability and relying on the collective action of all browser vendors to act as a check on any CA trying to break the agreed guarantees. But in a world where you would have a hundred, or even 20, different popular browsers, with different geopolitical assignments, it would be far harder to punish a CA that decided to sign certificates improperly, e.g. to allow some government or criminal enterprise to MITM communication.

Establishing identity in a non-centralized manner, and without requiring a second, already secure, communication method than the one you're trying to authenticate, such as an in-person key exchange, is in fact impossible, not just hard. There are partial solutions, with different trade-offs, such as the PKI for the web, the TOFU with optional verification options used in Matrix or SSH, or the web-of-trust model of PGP.