Cause and effect. The cause of righteousness is Jesus Christ: Jesus is the cause, and righteousness, love, peace and joy is the effect. The “other gospels” are where the true cause and source is bypassed, and man himself becomes the cause or source. Any other gospel is like trying to be justified by the law, it is futile. The offense of the Cross (Gal. 5:11) is that man cannot be the source of anything good, for if man is his own source of goodness then Christ died in vain, as a fool (Gal. 2:21).
The reason the true Gospel is becoming increasingly unpopular, and humanistic “gospels” are increasing in popularity is that no one wants to die. The offense of the Cross is that you die to your pride and you glory in another. You have nothing to be proud of or boast about or take credit for, and no basis to receive praise, glory and honor from man, except to boast in the Cross of Calvary (Gal. 6:14).