I absolutely agree that lack of life experience is a big contributing factor with these priests. The most capable priests I have ever met are those that have had a job, a career, experience living on their own in the world and making a living, dealing with adversity, before they have entered the seminary.
It shouldn't be necessary, and in the old days perhaps it wasn't so necessary, when family life was harder and involved more work and sacrifice for the whole family, the world was a bit less corrupting, and certainly less complex, and so a man could be adequately trained to cope with it by the time he was in his late teens. Nowadays though, despite the best efforts of Catholic parents who love their children and want them to save their souls, the task of a priest is more Herculean than ever, and a young man of 24 or 26, armed with no practical experience of making ends meet, no exposure to the reality of sin as he learns to associate with the same non-Catholic society his parishioners will be obliged to interact with on a daily basis, and no skill in judging people and character, has little opportunity to develop any of the skills that make a good household manager, personnel director, CEO, accountant, and all the other hats a priest has to wear today by necessity, beyond his biretta. He has 18 years in what is, we hope, a good Catholic home, with good examples and solid character formation, but where he probably doesn't take a big role in helping with the family business from an early age. Then he goes to seminary and spends 6 or 7 years learning a lot about theology and liturgy, which will, everyone hopes, ensure that he doesn't embrace one of a dozen big -ism's. He emerges from all this extremely well-equipped to teach theology and philosophy classes, fairly well-equipped to become a monastic scholar, acceptably prepared to fulfill the strictly spiritual duties of a parish priest, ministering to souls in the pulpit and the confessional, and woefully unprepared to deal with the temporal realities asked of him, to administer a modern parish, direct it's school, and so forth.
It's no surprise these perversions happen, and are allowed to continue, in that context. It's always easier to be conservative, preserve the status quo, close the ranks, and proceed slowly, if at all, instead of taking decisive action. And a slow, deliberate, methodical approach goes hand in hand with secrecy, giving us the classic "sweep it all under the rug" approach. A company that ran its operations thus would not survive, but the Church can get away with it because She has a monopoly on the most important product in the world: eternal salvation. Hence even if her priests are terrible, they usually don't have to tighten their belts. In the meantime though, errors and sins flourish, because the current system is much more geared toward producing good medieval parish priests (who didn't have to worry about much except teaching their flock well and managing the housekeeper) than the bureaucrats and administrators we need today.
Obviously there's almost squat we or the SSPX can do about this nowadays, as it's a problem that can only be resolved by a complete reconversion of society and a massive flourishing of orthodox religious orders. Be that as it may, the priests are obliged to do what they can. Some of them do it reasonably well, some fall flat. I do think, however, that old fashioned aloof clericalism of the autocratic Menzingen style does not help matters at all.