Someone did make an alternative to GnuPG called OpMSG, but I'm not certain that it is reliably more secure, other than not depending on an online Web of Trust / key server.

https://github.com/stealth/opmsg

The thing is it is less secure in many ways because you are giving up on reputability and using long-lives keys stored on untrusted devices.

Less secure than what? Unencrypted attachments?

The guy who wrote the OP is the guy behind Signal. That's the most obvious alternative.

But there's not a go-to answer because the lesson learned from PGP is that there can't be a single crypto Swiss army knife of a protocol. There are conflicting tradeoffs that necessitate the use of different protocols for different use cases. The best replacement for PGP is probably a basket of different protocols. See for example: https://blog.gtank.cc/modern-alternatives-to-pgp/