There are certainly situations where your opponents planned on attacking anyway, in which case Keldon Twilight is pretty meaningless
Having a way to keep a big creature on the board for the low cost of holding a single land open is an essential part of most formats, and Tamiyo's Safekeeping is one of the best you could tuck away for when you're in a pinch

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With new sets dropping rapidly every couple of months, tons of new cards enter the meta, which helps give older ones more support
exact top price depends heavily on condition and whether stamped