Some things you could add to your app are:
Regarding animations:
Parallax Scroll
Scroll Shrink (When the media height attribute decreases as you scroll down, like some banners on the Louis Vuitton USA website on mobile)
Regarding the header:
Make it sticky, but only when someone scrolls up, not all the time.
You could add the typical transparent header effect on the home page, and when you scroll down, it appears in a solid color, and perhaps the elements also change color.
You could keep the search bar like the original Shopify one,
with smart search suggestions, and have it work right there in the header without having to redirect to another page.
They could add another section when searching for templates, or sections called “Community Creations” or something similar, where users can upload templates or sections created after due review so they don’t upload just anything. This would help provide more variety in templates than other apps, as this is one of Instant’s weaknesses compared to its competitors. It would also make it feel closer to customers.