Ezekiel wrote down a detailed description of the temple that was to have been built.
If the people had been ashamed of their sins, then this is what they should have built.
One person has even built a scale model:
Nothing like that has ever been built. Nehemiah (or Ezra’s) temple was a poor substitute, and Herod’s addition didn’t follow the plan at all.
There’s some discussion about when this temple will be built. Some think it will be by Jesus after He returns; others think it will be as part of the last days; yet others think it will never be built. It was a plan God gave to Ezekiel for the Jews to build when they returned to Jerusalem, provided they had sufficiently repented of their idolatry. That they took so long to even get started, and needed later disciplining for their idolatry, intermarriage, and reluctance to get started on the building, suggests the true repentance might not have happened.