At some point, I also had some issues syncing notes between different iCloud accounts when the folder had 100s of notes, and that was probably the tipping point. As I was struggling to make it work, I kept thinking that if I just had a bunch of Markdown files I could move around, the whole process would have been easier.
I eventually realized I didn't need most features of Apple Notes, and moved to Obsidian[1]. It feels quite snappy too, and now I can easily publish some of my notes. It can also use iCloud Drive for syncing between Apple devices. It's missing some collaborative features, but I also didn't need those.
[0]: https://ricardoanderegg.com/posts/apple-notes-blog-cms/ [1]: https://ricardoanderegg.com/posts/apple-notes-to-obsidian/