Yes Notes is broken
See here and here and here, among other threads that discuss the situation. Apple broke AppleScript for Notes with Catalina and has done nothing to fix it.
Yes, Simplenote is also broken. Search here: there are other postings on this as well in this forum. Simperium (owner) blocks the integration now, and has for a few years.
For a moderate number of notes, or for notes that can later be exploded into multiple notes, Tot is a good choice. In recent days, Tot on iOS (and macOS) introduced a share extension. This increases Tot’s utility for collecting quotes, etc.
Evernote is also an option that so far has not been broken by its owner.