The poem to me seems to suggest a character who finds the somewhat narrow thinking and limited creativity in a church setting restrictive. He is a character who is presented as having immense imagination, and the way in which his creativity and imagination is met with censure from the church suggests that he needs to find an alternative location to be who he is.
The poet leaves the church through the power of his imagination to explore beyond what he has been conditioned to think. "Maybe I'll return when I'm ready" suggests that he will come back to the establisment thinking if he finds no resolution in his imaginative exercises.
Do you have a specific thing you want discussed?
In general, I think this is a poem about wanting to be a free thinker. My interpretation is that the speaker has no theological arguments with the church. Instead, he is rebelling against structure and rules in general. That is my interpretation of why he goes rising up through the church roof in his fantasy.
So it seems to me that the church, to him, is something that takes away fun (playing baseball) and creativity (the thing with the spacesuit). This is why he dislikes the church.
Thanks everyone for your thoughts, you presented a side I hadn't thought about. I was leaning more towards not liking the rules and bored with the teaching. Again appreciate your thoughts.