I have a pretty strict definition of alteration/cleaning and am really disgusted by the whole thing.
MTG altering (e.g., recoloring, trimming Beta corners to appear as Alpha cards, rebacking cards, etc.) has been around forever, but because most of the valuable cards were non-holographic, altered cards were always discernible for those with knowledge. It disturbs me that many (most?) altered holographic Pokemon cards are going through grading companies undetected.
Just due to statistics, I know with certainty that I must own at least one altered card. I think most collectors do as well these days, unless you pulled and graded all of your cards or only have cards graded from a decade ago. Because of this, I have considered on more than one occasion to sell all of my PSA 9s and 10s and to go back to binder collecting with played condition cards. At least then I will know that they are definitely not altered.
Until then, I will try to ignore the truth, and enjoy the cards for what they are. Owning polished cards doesn’t destroy the emotions and memories that I have made with them, nor does it destroy the beautiful art that draws me to them. In 2025, ignorance is bliss for Pokemon card collecting. If I think too much about it all, it depresses me, and I refuse to ruin my enjoyment of a (mostly) wonderful hobby over things that I can’t control.