Promises made and not kept are not the same as promises made that cannot be kept. Salvation, however, is not just about promises made. Hoo-nōs
Whether in politics, religion, education, economics, etc., etc., promises seem to be the food of hope and hope seems to be the cornerstone of salvation. Yes, it is important to listen to the difference in promises and how they unfold, but there are nuances. Promises made that are not kept could be for a variety of reasons from laziness to shifting landscapes. Promises made that cannot be kept may range from sheer meanness or duplicity to comforting those not ready for impending reality.
However, the cornerstones of salvation are not simply nested in promises, but at least in integrity, courage, work, and rest.
Be careful of those who promise—watch their behaviors. And watch ours. Promises and salvation are not shelter from the storm, and those who espouse it as thus as well as those who buy it as thus, are both deluded.