In Haggai 2:10-17, the Israelites were building the Temple of the Lord but their hearts were still far from God. In verse 14, God used “this people” not “my people” to distance Himself from them. The same way when Israelites created a golden calf from Mt Sinai God used the term “this people” and not “my people”.
Before the movement of the Church happens, there must be a movement from within first because God cannot endure inequity in the assembly (Isaiah 1:11-13). God is not pleased with sacrifices if they come from unclean heart and that what is God telling to the Israelites in the book of Haggai. No matter how much they did, how much they build the temple their efforts were in vain because what matters is the purity of their heart.