Good answer -
Perhaps part of the problem is that I see the Church holding these people to the same standard expected of a fully Catholic marriage (In the Church, proper preparation etc.) when in fact, we have NO idea, in many cases, of the particulars of the “marriage” in some other church.
So - While the Church accepts protestant standards for “marriage” (until proven otherwise) without knowing the particulars of proper preparation, intents and so forth, the Church will NOT accept protestant “annulment” (not a proper term, but bear with me here).
A couple gets married in a Protestant Church. All is good. Later they get divorced and this protestant Church, as a matter of form, accepts civil divorce as valid, so as far as they are concerned the previous marriage never existed. The woman remarries in her protestant Church…thus proving by act that this church accepts that the previous marriage was invalid. In this case, neither the church, the pastor or the couple believe that they are in an adulterous relationship.
Now this woman AND perhaps her husband, seek to convert to the Catholic Church. But the Catholic Church says - wait a minute…
Your previous church has the right and authority to marry in whatever way and by whatever standard form they might wish to apply and we will accept that, but not the right and authority to annul said marriage by whatever standard and form they wish to apply.
The people involved do not feel that they - in their current circumstance - are in an adulterous situation, and how they arrived at this situation occurred outside of the full understandings that we hold in the Church.
It just seems odd to try to hold them to the same standard as would be expected of a “Cradle Catholic” raised and married in the Church (as I was)
Now the situation above is a very “clean” one with no “church hopping”, something not uncommon in the protestant world. Combine this practice of “Church hopping” with the depth and requirements presented in the annulment process and one has a recipe for much difficulty and delay. Imagine trying to track down witnesses, friends, etc who knew you before during and after the marriage.
I do ramble a bit don’t I…

I guess that - in summary -
I feel a frustration for those who wish to enter the Church - becoming full fledged and devout Catholics and leave behind ALL of their past life outside of full communion with the Church.
I wish that the Church had a different, more streamlined set of rules that would allow these matters to be addressed in an expeditious manner of weeks rather than months so that such people are not held in limbo.
I feel bad because I know how “jammed up” the Tribunal process is in this country today and undoubtedly this requirement of the Church is part of the problem.
I just wish the Church would say that - when you come home and enter the Church, on that day - All before is moot. You are a new Creature, a new man/woman and we begin today as your new birthday - the day of your rebirth -
Then, because they are “reborn” they were never married before…

and their current marriage is blessed by a quick renewal of vows and they move forward…
Thank you for your patience with me…
Peace
James