Ridiculous. A rifle, and the protagonist's skill over it isn't thematically significant? The protagonist's steady improvement and mastery of its use isn't thematically significant? The rifle might be very personal, might have a very interesting history with the protagonist.
None of it makes any difference. None of it makes it okay to have a story with no climax, by having the protagonist shoot the antagonist in the face with no struggle. Whether the rifle is a person heirloom wielded by an expert or a piece of junk picked up 15 seconds ago by a novice. A story without a climax is a story without a climax.
Contrary to what you might think, the fact that the Anchor is stuck to the Inquisitor makes no difference. Nor the fact that's it's magic. Particularly in a world where the magical is the mundane.
No, the real issue here for you is that anything more complicated than the protagonist walking up to the antagonist and lopping his head off with a sword might threaten the Inquisitor's reception where everyone showers him with praise for being the best person ever. We can't have that. Oh, my mistake, I mean showers you with praise. Isn't that right?
A rifle can be thematically significant. Let's take the most obvious hunk of magic metal here: Excalibur. What makes it significant - beyond the fact that it's really good at being a sword - is the mythos that's built up around it. Your argument fails because its premised on how mundane a rifle is in the abstract - but any mundane object can become thematically relevant based on the plot.
If you write a plot about a sniper battle, with the protagonist steadily improving over the story, only to use a broken down and ancient rifle to take down the antagonist, then certainly that rifle becomes thematically signiciant. Again, I question that you have any understanding as to what "theme" means or what makes a conclusion thematically important.
As always, I will ignore your personal attack.