The Thriving Lands
Thriving Bluff, Thriving Grove, Thriving Heath, Thriving Isle, & Thriving Moor:
I can see a case for having these side by side with the the Baldur's gates for great colour fixing, but this cycle of land just can't compete with the extra utility on the other dual lands. These lands would thrive in a cube that would have more multi-coloured cards or where you want to replicate the scarcity of colour fixing and only having these.

Emerge Unscathed:
Unfortunately this card did not come out untouched. The built-in 2 for 1 is great but rarely does it make any meaningful impact on the rebound. Blessed Hippogriff will be taking its spot, as it has the protection on the adventure side. It being an evasive attacker that can also pick up another body is a boon to aggressive decks.

Knight of Old Benalia & Tah-Crop Elite:
The number of mini anthem effects has grown over the years that these cards no longer stand out as creme of the crop. While still being very powerful cards in their own right, they are being cut in favour of cards of a different flavour. Ones that bring utility and can attack from different angles besides turning your creatures sideways like Guardian Naga and Pegasus Guardian.

Martyr of Dusk:
It's time to put this card to rest. There are plenty of targets that make good sacrificial targets that there is not much to be lost here.

Dreamtail Heron, Soulknife Spy, & Wretched Gryff:
These cards are being cut in favour of the new blue adventure creatures. They all fulfill the same space as a large evasive finisher that also cantrips. As such they will be replaced by Young Blue Dragon, Sea Hag, and Goggles of Night.

Narcolepsy:
Stunning Strike is a stellar overperformer and is definitely not a card to sleep on. While it does cost 1MV more, the flexibility to slap this on one of their biggest hitters on the opponent's turn makes it a better fit for control-style decks that like to play land-go style.

Clutch of Currents:
Sword Coast Serpent has taken hold over Clutch of Currents position as the cheap bounce spell with a big body. Sword Coast Serpent has the greater edges as you can play the adventure side for cheap and not lose out for holding back the spell to get a body. You can hold onto the creature side and not worrying about losing the flow of the game.

Adventurous Impulse & Grapple with the Past:
It's hard to tackle good cards like these but I believe Druidic Ritual has done it. It's time for these card to take their place in the history books of good graveyard enablers and cantrips, especially in green which for so long had not been very good with maintaining card advantage.

Jungleborn Pioneer & Twin-Silk Spider:
Replaced with better token generators. Losing the hexproof on the token does suck but this is for a healthier and better gameplay as hexproof has shown time and again it can be quite unfun.

Warteye Witch, Nested Shambler, & Hoard Robber:
Warteye Witch and Nested Shambler are being sacrificed for more improved tools. Nefarious Imp is a strict upgrade as it can trigger off more than just your own creatures dying. There is a whole host of fodder targets, that Nested Shambler did not have a home to stay in. I can see it making its return back in the cube if more incidental pump spells were introduced. Despite its name Hoard Robber wasn't able to steal the show. There weren't enough moments where it could produce any treasures.

Chainer's Edict & Evincar's Justice:
They have been removed from being flexed on by Arms of Hadar. While it doesn't have the late game repeatability as Evincar's Justice, it does a phenomenal job of only killing your opponents things. In time Evincar's Justice will make a return.

Keldon Marauders & Inner-Flame Acolyte:
As they say two's a couple and three's a crowded, and it surely is crowded in the 2MV and 3MV slots in red. Both of these creatures are excellent enablers in the aggressive red strategy, however this cube is branching away from narrowing the colours into one strategy and opening up for more fun options.