What makes the Notion illustrations so appealing and effective to me is not their style, though I love the way they look, it is that they are created for the need at hand. They are individually made to a purpose.
Side note: I manage several illustrators for a team that produces educational media and one of the hardest things we have to communicate to users is what an illustration is good for.
I have users come to me with an image and say, "I want an illustration that looks like this."
And we ask them, "But what do you want the illustration to do."
And they answer, "We want it to look like this."
They don't have any particular purpose for the illustration, it's just wallpaper for their website. A way to break up a page. A function of general art direction, rather than a working part of the content.
We end up doing a lot of what amounts to custom clip art, because that's what users often want. And it really does help a website or a video, or a document to have consistent art direction. But by far the the most compelling and engaging content we work on isn't from when a user asks for a set of stock images and icons, all in the same style, but it's when they comes to us and says, "We have this problem explaining this idea, or telling this story. Can you help us with that?"
