Ring Around The Sun It's very homogeneous.
If the purpose of the piece is some pleasant background music than you've achieved your goal. The melody is simple, catchy, and light. But, a background needs to have something else going on in order to not become boring.
By being so light, it feels generic and unoriginal. It's not my place to write your piece for you, but I'd do much more with the melody. Honestly, as I was listening, I kept waiting for a new melody, or perhaps a change in the one you already have. I'm not recommending you layer anything, since that's very difficult to do while still keeping the piece light and airy.
But if you could pull off a few subtle changes, like the instrumentation of the second melody layer around 1:53 it would help fit with the shifts in tone you made at 1:37. I feel that I should comment on the rhythm of the piece too, but honestly everything I just said about the melody applies to the rhythm also.
A lot of why the piece is so homogeneous and generic is the fact that you don't change really change anything throughout the entire piece, you only change the instrumentation, which makes it sound like a cop-out. It's almost too easy to write a music like this, which is why everyone does it. And why they all sound alike.
I don't mean to be cruel, it's just that it feel like you put more effort into creating a particular type of sound, rather than writing a more effective melody or rhythm. There's no real variation in this piece and as happy as the melody is, it's nothing more than a light filler.
I'm sorry if I sound too critical and I hope you don't think I'm trying to be insulting. It's just that I could see a lot more being done, but that's only my opinion.