It has too many confusing features, and you don’t have to use any of them if you don’t want to. The core of public keys, signatures, and both symmetric and asymmetric encryption are solid. Just like if I write simple HTML, it will work in 20 years worth of browsers.
Few technologies can boast this type of lindyness, and I appreciate them a lot, especially when I can actually make use of them.
If you are wondering how to openpgp these days, many use cases are well covered by SOP, which is a simple stateless interface specification with multiple mostly drop-in swappable implementations: https://wiki.archlinux.org/title/Stateless_OpenPGP
One interesting thing is that there's a test suite checking implementations developed alongside the spec (https://sequoia-pgp.gitlab.io/openpgp-interoperability-test-...) so it's easy to see the conformance status.