There's an entire book devoted to ripping up the OSI model: https://docs.google.com/document/d/1iL0fYmMmariFoSvLd9U5nPVH...

X.509 absolutely lives on -- https://www.itu.int/rec/t-rec-x.509 last update was October 2024. However WebPKI uses PKIX which is fairly stubbornly stuck on RFC5280.

On the ITU side, they have made improvements including allowing a plain fully qualified domain name as the subject of a certificate, as an alternative to sequence of set of attributes.

If you mean the presentation layer, hard disagree. Not thinking about presentation creates problems. For example, Go treating ASCII headers as UTF-8 caused trouble. Only slightly not worrying about an HTTP/2 vs HTTP/1.1 mismatch caused trouble for reverse proxies.

Now I'm young enough not to have seen teletypes in an actual production use setting, but I've never heard anyone suggesting the presentation layer was for teletypes. That's just Google-level FUD.

  X.500 was stripped down to form LDAP

No, LDAP was a student project from UMich that somehow gained mindshare because (a) it wasn't ISO, and (b) it cleverly had an 'L' in front of it. It's now more complex and heavyweight than the original DAP, but people think it isn't because of that original clever bit of marketing.