The focus of Psalms Book IV and the Summary Psalm 149 is on the work of the glorified saints in serving as mediating priests under Christ.
The Millennium or God's rest will be an exceedingly busy time, a time when all of humanity will be converted, a time everybody will be on the same trek.
The Sabbath is an antidote to the weariness we experience. It recalls God's pausing after completing His physical creation, focusing on the spiritual creation.
The ancient Israelites resisted the gospel, refusing to mix it with actual obedience. What they heard never became a part of their lives; Egypt never left them.
If we patiently endure, trusting in God's faithfulness to bring us to completion, there will be a time when we will attain the rest we desperately yearn for.