There are two sides to all of this -- the faith and the Mass.
If you really believe that Vatican II was the entire cause of loss of faith, essentially you are saying that God willed evil on His faithful and holy people. This is why I do not buy the argument that everything was dandy before Vatican II and that Vatican II was some out-of-nowhere bombshell that ruined a thriving Church. I see it as more of a punishment.
The faith was slipping long before Vatican II, many people were already ecumenical, many people had a "contraceptive mentality," many people were going to quickie fifteen-minute McDonald's Masses. "This people honoureth me with their lips: but their heart is far from me." There was an immense pressure on the Catholic Church to get with the times, to modernize, to stop being reactionary and fuddy-duddy. The very concept of tradition and of the unbending Rock had been nearly forgotten.
Vatican II simply gave people what secretly they already wanted or thought they wanted. Then they realized they didn't want it. Because to be in Vatican II is to bend God's rules to the level of man. But if you're going to do that, why go to the strictest Church, the true Church, the Catholic Church, at all? There is a contradiction here -- the Catholic Church is for those who want the truth, who want to know God's laws, no matter how harsh. Take that away, and you just have another sect.
So the lukewarm were filtered out, a new group of nominal Catholics who are really kind of agape, Protestant-like faux-Catholics filtered in, and the only Catholics that remain in VII are those who simply ignore all the changes, and even they stand a good chance of eventually being infected by the "new ways."
At the same time, the watered-down Mass is where the atomic bomb was really dropped. I do not think this is the abomination of desolation anymore, but it's a foreshadowing that removes or diminishes the most necessary source of grace. This repulses the conversions of those with a lofty spirit, and undoubtedly has driven many to leave what they think is the Church. In my pagan days, seeing what the "Catholic Church" had become, with little effeminate hippie folk-singers chanting Kumbaya, I certainly had no desire to be Catholic. I thought it was pure cheese. But eventually God brought me in.
To sum up: It's all connected. It's not ALL about the Mass, but that is one of the biggest parts of it. Essentially, in the new Church, everything has been replaced by dummies and impostors: You have dummy monks, dummy nuns, dummy saints, dummy miracles, dummy Popes, and at the center of it all, a dummy Mass. It's like a movie set at Disneyland, not the Church.
God is undertaking a filtering process; He is separating the men from the boys. In our time, only those who work extremely hard to find the truth will attain it. God has had enough of the lukewarm, and He is spitting them out of His mouth.