big drawback to the Skyrim Anniversary Edition being an upgrade to Skyrim Special Edition, instead of a completely separate version of the game, is that the new edition can break your mods. Even if you didn't buy Skyrim AE, you may still experience mod incompatibility due to Bethesda's update to the Special Edition...
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This mod rolls back Skyrim Anniversary Edition to Special Edition version 1.5.97
Source: PC Gamer (opens in a new tab)