Nip17 is a combination of nip 44 and nip 59 gift wraps, which takes care of the concerns in that message.

NIP-59 seems to do a good job at hiding metadata from public view but it doesn't provide - break-in recovery. - repudiation (deniability). - (lack of) visibility of connection graph to observers. - fixed message sizes (although it can be provided by the specific app) - resistance to Shore algorithm (PQ encryption). I can add that it definitely doesn't provide forward secrecy. It's concerning that these developers simply don't seem qualified to properly implement secure messaging, and I believe users are being put at risk, although I do see a lot of people just putting @SimpleX Chat addresses in their profile anyway.