I have seen serious priests with doctorate diverge on these issues.

First, the law has to deal with measurable stuff, not internal thoughts.

John and Mary want to marry, finish the required courses, say the right things: how would the church know what is inside their heads?

the presumption is that whatever happenned under the right form is valid, and that people above the required age understand and mean what they say.

Second, I doubt many marriages really need to be redone even if shitheads were too immature to consent. Imagine:

Joe married, but he is so badly cathequised, so lacking of good examples, that his shithead was unable to grasp concepts like "forever" or "open to life". He did the required classes and said the required words. Some went totally above his head, some he rationalized like "this stuff is old fashioned talk, nowadays we have evolved, we are free, modern, this is all just a theater for grandma..."

After some years, he matured. Children come. Some day, Joe realizes for real he really wants to grow old with her, not anymore "just while I like her and she is cute".

Now they have the intention, the consent. The form, the cerimony, is positive law, it was not even required before Trent.

On their next intercourse, their marriage is consumated. It is the intent + intercourse that makes a marriage anyway after positive law is fulfilled - and their marriage is on the books. No need to fix what is not broken.

Anyway, if they consciously see their own change, they would profit from a quick reconfirmation cerimony during a mass - and it would dissipate any doubt or scrupules.

what really matters in practice is when they divorce and want annulments. How to judge what was inside their heads?