You take a pragmatic view of the Mass -- what's in it for me? The Mass may help us get to heaven, but that's not the essential nature of the thing. The essential reality of the Mass is that it is Christ offering Himself to the Father as both priest and victim. This is higher even than heaven.
This makes it seem that God is needful of these things from us.
Only if you misunderstand it. As you say, you can claim that "the universe exists to show forth the glory of God's own loving goodness," and this is not contradictory with the statement that the universe exists to offer praise, honor, glory and worship to God. Which one is its end? Creation by the fact of its existence displays "the glory of God's own goodness," but the purpose of that creation, the teleological orientation inherent in its created nature, is to give back to its creator the worship that is His due.