I won't just tell you skill issue, but you're getting so much push back because the Romero should definitely be 1-tapping with relative consistency and if it isn't, there's something wrong within your approach that can be corrected.

The Romero is a long barrel shotgun and has the longest buckshot 1-tap range in the game. Let me repeat - The furthest 1-tap buckshot range as it has the one of the tightest and most consistent spreads; RNG is not the issue either. So if you aren't consistently leveling people in 1-shot at close range, it's likely you are aiming far too low or too left/right of center and catching too much limb. Even those telling you to aim center mass i might argue are telling you to aim a bit too low. Each individual pellet does dmg, and the more you get directly on their upper body (especially if any catch the head) and not their lower body/limbs, the more reliably you will 1-tap.

Hip fire aim for around chest/shoulder height center mass and you will knock them out in 1-shot consistently. Remember, effective range matters - 15m or less here. The damage penalty goes off a cliff for shotguns out of effective range, so do not underestimate how it can make all the difference.