Look at the bookend statements of Psalm 100.
It begins: “Make a joyful noise to the LORD, all the earth!”
And
It ends: “…his steadfast love endures forever, and his faithfulness to all generations.”
ALL the earth and ALL generations.
Not some parts of the earth and only favorite generations.
The capacity of God’s love and faithfulness toward you and me is not questioned by the psalmist.
What is legitimately questionable is our willingness to accept his invitation, to “Serve the LORD with gladness” and “Come into his presence with singing.”
It isn’t really optional if we want the abundant life he promises.
The thief comes only to steal and kill and destroy. I [Jesus] came that they may have life and have it abundantly.
John 10:10 (ESV)
This is where our greatest battle in life is always waged. Everything else is a designed distraction to include politics, health, wealth, and every other possible relationship to include conflicts and even the good times.
For we do not wrestle against flesh and blood, but against the rulers, against the authorities, against the cosmic powers over this present darkness, against the spiritual forces of evil in the heavenly places.
Ephesians 6:12 (ESV)
Because this is true, our warfare is spiritual and begins with an allegiance to one side or the other. We join God in the battle as we submit to his leading and his power to wage the war for us and through us.
Make a joyful noise to the LORD, all the earth!
Serve the LORD with gladness!
Come into his presence with singing!
Know that the LORD, he is God!
It is he who made us, and we are his; we are his people, and the sheep of his pasture.
Enter his gates with thanksgiving, and his courts with praise!
Give thanks to him; bless his name!
For the LORD is good; his steadfast love endures forever, and his faithfulness to all generations.