There are entire strategies that simply wont be able to survive the rotation as the entire core of the deck rotates
I've always been about the art and flavour of TCG's, and as you can see from the contents of this blog, the fact that a huge chunk of MTG has been about monsters and creatures meant that there was plenty of content for me to talk about
Specifically, Sword of Fire and Ice gets the nod in Legacy because protection from blue allows creatures to attack through True-Name Nemesis, red covers a section of cheap removal, and the trigger says draw a card. In modern I suspect many of the other swords will get their chance to shine: the protections are more relevant and cover different Modern archetypes
You can only use 1 "Tidal, Dragon Ruler of Waterfalls" effect per turn, and only once that turn.
The issue with the player experience counters, is that the traditional routes of dealing with it aren't there