I would honestly cut
Mythos of Illuna and two artifacts to add one red and two green cards. This would give you:
51 white
51 blue
51 black
51 red
51 green
15 Dimir
15 Gruul
15 Orzhov
15 Boros
15 Simic
3 Esper
3 Naya
3 Mardu
3 Temur
41 colorless
50 Guild lands
10 Triomes
4 All-colored lands
Then I would move the colored artifact cards to their mono section and look at the only beautiful cube in the world
You could maybe even go crazy and cut 1 of each mono card to include 4 more artifacts and 1 more All-colored land.
50 all each mono
15 of each Guild
3 of each Shard
45 colorless
50 Guild lands
10 Triomes
5 All-colored lands
The most beautiful <3
I bet you could find a way to balance each archetype, deck and theme this way still by changing some cards.
You are 8 card changes away from this.