Superficial Devotions are Sacrilege – Temurah

We are not permitted to upgrade a beast we designated as a sacrifice, by swapping it for an alternative, fatter, more splendid looking beast.
Why not? Is it not a signal of our devotion that we wish to offer a superior sacrifice?

Perhaps the reason is that an excessive focus on the externalities of our service to Gd is in fact a decoy that misleads us and takes us away from true service to Gd.

Is it not possible that this is true of other devotional matters?
Perhaps our obsessions about various superficial aspects of our devotions are in fact decoys that mislead us and take us away from true service to Gd?

But there is something wrong with this as we maintain that one should always pursue Torah and Mitzvos, even SheLo LishMah, since eventually we will be won over and will come to our senses. So, would it not be applauded to also upgrade our sacrifice?