For all of their nerd cred, key parties didn't accomplish very much (as evidenced by the fact that nothing on the Internet really broke when the WoT imploded a few years ago[1]). The "real" solution here is mostly cultural: treating third-party software like the risky thing it actually is, rather than a free source of pre-screened labor.

[1]: https://inversegravity.net/2019/web-of-trust-dead/