It’s okay to copy.  Ivan Zhao said on an AMA forum,  “Our guiding light has always being history. To be honest nothing is new in Notion. We copied everything from earlier systems.”

Most of the time, all I was doing was imitating my favorite authors, anyhow. I went through a Hemingway stage (who doesn’t?), but I also went through a pretty serious Annie Proulx stage and a rather embarrassing Cormac McCarthy stage. But that’s what you have to do at the beginning; everybody imitates before they can innovate.

When you steal, don’t just copy and paste the work of your predecessors. Once you have mastered the form, bring those influences together in a new way. Curate before you create. If you do this well, you won’t be merely cribbing other people’s work and passing it off as your own. You will be building on it and making it better.