page layout - Illustrations showing up pixelated in Indesign despite huge resolution

Illustrations I create in Procreate show up pixelated at edges despite high resolution when I place them in Indesign.

I'm working on illustrating books for print. It's my first time working on a print project, I usually do digital illustration for the web.

I use Procreate on Ipad Pro for illustrations, and need to place them into Indesign layouts. I do my best to create clean lines in my illustrations, and use a huge resolution as well (each illustration is about 3000x3000px in size), but when I place them in Indesign there's some weird stuff happening with illustration edges. I use 4000x4000 at 300dpi resolution for my canvas. Then export the image as PNG before placing into Indesign.

What am I doing wrong? Maybe it's exactly because the resolution is too high? Or it's a PNG issue?