0:40 onwards really caught my attention

The sound in the beginning was very light-filled and sparkling, like the sun

It is a tad repetitive, but that can easily be changed with variations. I think the reason some people are saying it sounds simple and thin is because most of the time you have only one instrument with an outstanding melody. Having some counter-melodies might be something you'd enjoy experimenting with.

All in all, I liked it!