I think you’ve found most of the existing solutions, sadly: effort. When I imported from Roam (and I was lucky to not have a lot of items) I had to find and replace a lot of things, especially indentation and bullet-items.
For what it’s worth, BBEdit may be your best friend. It has incredible find and replace capabilities that operate over e.g., a specific selection of plain text files, or all open text files, etc. Try the free trial. It may be all you need!
If you mean natural language dates, I believe @argentum already has a plugin based on the new and shiny API for this: GitHub - argenos/nldates-obsidian: Work with dates in natural language in Obsidian
NotePlan 3 or 1Writer are your best options here, in my opinion.
This is tough for now, though I think we’ll see some export plugins very soon. Until then I export to iA Writer, clean up the brackets, and go from there.
Also, not migration-related, but see Using (and automating) Obsidian on macOS - Meta Post.