Instead of saying, “Let them build Me a sanctuary and I will dwell in its midst”, God promises, “…and I will dwell in their midst” – i.e. in the midst of the builders.
Why doesn’t He speak about inhabiting the building? Because He spans the whole universe, and no edifice, however grand and beautiful, can contain Him.
It is strange then that the Tanach calls the sanctuary Bet HaShem, the House of God, and to this day we speak of a synagogue in the same way.
The description is understandable but rather problematical. The fear in Biblical times was presumably that people would think that the sanctuary was God’s dwelling-place whereas the rest of the world was not His domain or concern. We had to be warned that (as Psalm 24 tells us), “The (whole) earth is the Lord’s”.
We have the same problem today, thinking that the synagogue (and nowhere else) is where to find God.
Result? As Eliezer Berkovits says, the Almighty is like a prisoner locked up in the synagogue, visited at set times and wholly divorced from the real business of daily life in the world at large.
Having synagogues is nullified if we leave God behind when we go home. The only way to make the sanctuary meaningful is to carry God and His message with us wherever we go.