Protestants don't 1) have daily Mass; 2) don't have a 'sacramental system' AND 3) never did have churches as large as many of our Catholic parishes.  Their cathedrals had larger numbers of members, but not in smaller towns.  Most Protestant ministers were married for centuries---so being married is NOT contributing to the decrease in main-line Christian churches.  

Sure, the main-line Christian churches have problems---but they also have some interesting structures to deal with these problems that involve conferences of the laity as well as clergy and bishops.  Our bishops could take note of that.

You stated there are larger numbers in graduate[Catholic] seminaries.   Women and men in graduate classes of theology, history of theology, church history, etc. outnumber the 
priests seeking doctorates more than 3 to 1---places like Boston College, Weston Jesuit School of Theology, Creighton University, and Santa Clara Univ.