Vico, this is the same discussion you and I have had on other threads. I think you overestimate how much the average Catholic understands about what they are doing. I would say 70 to 90 percent of Catholics doing a Divine Mercy devotion for Divine Mercy Sunday at church don’t understand that Jesus’ grace and the indulgence are two different things. Unless they read Susan Tassone’s books, they likely have very little understanding of indulgences in general, but might get one when the priest, as he sometimes does, announces one is available and lists the conditions. Also, often the bulletin or flyer for the Divine Mercy devotion will try to include info abut the benefits of DM devotion and very often the info is confused or misleading.
In any event, here is how I’ve seen people go to confession for Divine Mercy devotion day: they show up at church for the devotion, they see there are 3 or 4 priests hearing confessions, and most of the people get in the confession line. A few of them may be thinking of getting the indulgence, many of them are just assuming the confession is a required part of Divine Mercy Sunday because priests are there hearing them, still others are motivated by monkey-see monkey-do “everybody is going to confession, I better go too” and a handful might even have the mistaken old idea that they need to confess within a week before or after Easter for “Easter duty” and they didn’t get there before Easter.
The last time I went to a DM devotion, I was one of the few people NOT getting in line for confession because I’d already gone the day before. They had 4 priests who heard confessions for about a half hour before the devotion and a couple who kept it up during the devotion and I’m guessing probably 80 to 100 people confessed, probably 3/4 or more of those in church.
I have also never met anyone who said “well, I don’t need confession because I just rely on God’s Divine Mercy.” The people who do Divine Mercy are generally confession-goers even if they only go a couple times a year. Those who don’t confess also don’t bother with devotions and in addition don’t feel they need mercy from God because they either think they’re not sinning or they think God understands everything they do and gives them a free pass. They never think of themselves as bad and sinful enough to need mercy.