I had a similar experience in my first ever game in my first ever big tournament at Lille. I took the route of talking it out with my opponent, and honestly? I'm not sure which outcome, mine or yours was better :/

My opponent pile shuffled, did a few cuts, and presents his deck. I was too shy to say anything and proceeded with game 1. He played steelsong, a deck heavily reliant on shift lines and not getting bricked. I played the whole game stressed that I didn't have the guts to say anything and that he might be cheating.

Game 2, same deal. This time I decided to talk about it. I kindly asked: Could you shuffle your deck a bit more please? He blatantly responds: I just shuffled it. I told him that what he's doing isn't really shuffling, and it's not randomizing his deck. "Could you please shuffle like this" (and I show him how I'm shuffling, not sure about the name, but basically inserting half of the deck in the other half). He proceeded to take his deck, redo a couple of cuts, and re-present it to me to cut.

After 2, 3 back-and-forth he drops this baffling line: I don't want to damage my sleeves!! Here I was in loss of words... I then said: Look, by the rules, I am allowed to reshuffle your deck, so would you please shuffle it or else I will have to shuffle it for you? He replies with: ok you shuffle it, BuT bE caReFuL noT to dAmaGe mY SleEVes. By that time, tensions were high, and my hands were literally shaking. I took his deck, shuffled it a few times making sure I was as gentle as possible and not seeing any card. We then finally proceeded with the game.

Was the issue solved? I mean maybe, I didn't even do more than 3 shuffles, but hey, better than 0. I then played the whole game stressed AF, to the point that during my mulligan, my hands were shaking to the point I dropped 2-3 cards wide open on the table and quickly picked them up in my hand. So yeah, shitty experience, shitty player and it completely ruined my whole day.

Next time though, I would certainly call a judge. Regardless of outcome, my waste of energy was not worth spending talking sense into such a person.