Strict Constructionism

The second entry in a trilogy is often the most divisive.
Most of us don't think of the Torah as a trilogy: it's one scroll, containing the Five Books of Moses. However, both the Talmud (Shabbat 116a) and Midrash (Genesis Rabbah 64) insist that the Book of Numbers should not be seen as singular; leaving Mt. Sinai represents an irrevocable shift in the narrative. Indeed, if we look at the Torah in terms of the 54 weekly readings, the 18 which follow the departure from Sinai have a common theme: asymptotically approaching the Land of Israel.
Numbers is not the only book which has a split personality, though. We are smack in the middle of the Book of Exodus, and one can't help but notice how the Exodus part of it abruptly ends halfway through. The first six portions tell the dramatic journey from slavery to Sinai, a story so good Cecil B. DeMille told it twice. It is, in many ways, the culmination of everything established in Genesis, the fulfillment of many of God's promises.
However, starting with this week's portion, Truma, the main focus is not the tribes of Israel or the territory of Israel, but the Tabernacle. For eighteen portions, the Torah details every aspect of the Tabernacle: how to build it, what to offer, who works there and in what capacity, when and where one is allowed to enter. The setting is unchanging, and the only narrative breaks deal with the great joy of constructing and consecrating the Tabernacle (and the violent deaths of any who defile it).
All Jewish studies teachers know this well. That's why once we hit Truma, the time spent on the weekly portion plummets, while the time spent on talking about the upcoming spring holidays swells. Even the Sages seem to recognize this by adding supplementary readings and doubling up the regular portions. But it's hard to jazz up these portions, even if you repackage them in listicles, such as "15 Items Every Tabernacle Needs!" or "You Won't Believe How Impure These 8 Animals Make You!"
Still, I can't help but wonder if there is an important lesson in these portions. The Torah describes in painstaking (arguably, painsgiving) detail every aspect of a structure which we will never rebuild. Even those who foresee a literal rebuilding of the Temple admit we'll never again need to know that the bronze sockets are for the courtyard pillars while the silver sockets are for the sanctuary planks (obviously), because the Tabernacle is passe. In fact, many maintain that some of the elements used in its creation, such as the tahash, were never seen before or since:

The tahash of Moses' day was a unique species... with one horn in its forehead, and it came to Moses' hand just for the occasion, and he used it for the Tabernacle, and then it was hidden.
(Talmud, Shabbat 28b)

And yet it is part of our history and a good third of our Holy Book. We do not discard or deny or defy it.
I was born and bred in the U.S., so naturally I think of the Constitutional analogy. This is a wholly human document barely two centuries old, but there are numerous clauses crossed or grayed out because they are no longer applicable. And yet they are still there, reminding us that Americans once thought it important to safeguard slavery or to prohibit liquor.
Judaism today is quite different from the Tabernacular version of Moses' day. Three millennia from now, who knows what our descendants will think of our religious priorities? Ultimately, the built-in obsolescence of the Tabernacle teaches us that a faith must grow and develop if it is to live on.