They are designed for Limited formats, give every player a fair card pool, and keep the opening experience exciting with foils, wildcard slots, and chances at extra rares
Grade Your Disney Cards Disney has recently celebrated their 100 year anniversary making their cards of late, hugely desirable
Kalemne otherwise sees lots of play in the 99 of other Commanders that care about Experience Counters like Kelsein, the Plague and Azlask, the Swelling Scourge
There are only a handful of people who have ever led the design of both a small Magic expansion and a large Magic expansion
Overall, I think Legends is a set that is not fondly remembered
playtesting forms the biggest population of proxy users when it comes to Magic: the Gathering