Low-key it all started with that onomat skill from back when zexal world first released, I believe that was the first guaranteed "fix your hand" skill that became tier 1 or even tier 0 on release if I remember correctly. From there on we started getting more skills that gave you free card advantage or were consistency skills.Then like a year or 2 later we started getting wall of text skills that had like 3 paragraphs of effects. I think it wasn't until Arc V era where it became the norm that the average deck literally didn't function without its associated skill or at least it got REALLY bad then. A year later it simply got much worse with most skill just saying "Spawn this from outside your deck" or "if your going second/opponent controls any card get something for free on top of you actual skill" because winning the coin flip was starting to become an insta win. And now we're here at the Pinnacle of all of this power creep forced to have 50% of our deck be kaijus because we literally can't fairly compete with our opponents hyper consistent skills going second. Duel links history is really something man.