those are not copies, they aren't even features. usually part of a tiny feature that barely works only in demo.
with all vibe coding in the world today you still need at least 6 months full time to build a nice note taking app.
If we are talking something more difficult - it will be years - or you will need a team and it will still take a long time.
Everything less will result in an unusable product that works only for demo and has 80% churn.
Bad example, note apps loaded with features are anti-productive and are for people who treat note taking as a hobby itself.
You have Obsidian anyway if you want something open source to work with.
When everyone is able to make their own one off prototype in 30 minutes, no one will pay for the thing that took someone 6 months.