In addition to the above, I'd also argue that Death's Shadow itself is much weaker as a card when it isn't surrounded by a tempo-oriented shell. A big dumb critter without evasion will actually be pretty ineffective in a lot of boardstates, for instance when it's staring down a board stall. If the opponent has a medium sized Goyf, ScOoze, a True-Name or some random assortment of chump blockers like Snapcasters with you at 5ish life your Shadow is mostly going to be on defense, though due to the life total situation your opponent is more likely to draw out of the stall and win. The best way to leverage Shadow as a card to me has been being aggressive and putting down so much pressure that your opponent needs to chump as early as possible. It only really wins races if you can force chumps, as a rule of thumb. And if you do get into board stalls between your Shadow and Goyf-like creatures your best win condition is usually a Delver flying over for 3 every turn, something the slower build is absolutely incapable of.

That paired with the facts that JVP s not a Legacy playable card and that Hymn is a medium powerful value card that doesn't really have a place in a Tempo deck, plus the fact that There have been no notable results for the slower build speak for itself imo.