NOOO! The pf-editor-service endpoint has been a godsend for me for converting various content to ADF format, and its sudden demise is bad news for me too.
The purpose and use of that endpoint was never really explained anywhere. It would be really, really, really great if Atlassian would make a public announcement as to what it was for and what, if anything, it will be replaced with. In the absence of good open source tools or cross-language libraries for creating or converting ADF content, it really is a outlier standard that can be painful to deal with.