When they make mood music for troubled grown-ups, the progressive-pap journeymen in Mike + the Mechanics really aren't all that horrible. ''The Living Years,'' their 1988 chart-topping eulogy to the father of Mike Rutherford leader of the Mechanics when he's not playing guitar with Genesis was uplifting in a thoughtfully maudlin way. On their new album Word of Mouth, in ornate soap operas like ''Let's Pretend It Didn't Happen,'' the Mechanics let their synthesized bombast breathe comfortably. ''Before (the Next Heartache Falls),'' with its military drums, funk guitars, and falsetto vocals, is hardy soul-schlock worthy of Phil Collins, the most famous and talented Genesis graduate of all. When the group tries to rock hard, however, it sounds generic, and hopelessly flabby. Now that Rutherford avoids cynical jokes like 1988's ''Seeing Is Believing,'' in which he sarcastically pledged his faith to everybody from Daniel Ortega to a gun-toting Jesus, his lyrics have become as vapid as any advice column. But just like every other millionaire to emerge from Genesis' fertile fold, you can tell he's a nice guy, and that's worth at least a...B-.