Dear Wizard,
I'm an old Magic Player and UX Designer specialized in gamification. I'm writing to you to share some consideration about Magic Arena.

The most popular opinion about Arena right now is that: Alchemy was a mistake, digital cards are stupid and they are ruined the Historic format. The Arena Championship has had far less total views than the ProTour Phyrexia and Arena events of past years. To fix this you could consider the following advice:

There are a lot of iconic/strong cards on Arena that you cannot play in any format like Teferi, Time Reveler, Misha's Bouble, Counterspell, Lighting Bolt, Ragavan, etc; you can create another format - called "Arena Classic" for example - where players can use all the paper cards into Arena with all the cards playable in Modern or Legacy (to include Minsc and Boo, Timless Hero, etc...) and add this carefully studied cards list to create the best and nostalgic Magic format ever:

Mythic

Vendillion Clique
Jace, The Mind Sculptor
Kiki Jiki, The Mirrorbreaker
Batterskull
Karn Liberated
Vengevine
Sun Titan

Rare

Dark Confidant
Timeless Dragon
Bloodghast
Vindicate
Stoneforge Mystic
Birthing Pod
Walking Ballista
Gravecrawler
Cryptic Command
Valakut, The Molten Pinnacle
Flagstone Trokair

Uncommon

Wall of Omens
Smallpox
Dismember
Spell Snare
Remand
Flametongue Kavu
Warping Wall
Kitchen Finks
Street Wraith
Path to Exile
Flame Blitz
Wear / Tear
Tidehollow Sculler
Gerrard’s Verdict

Common

Spreading Seas
Arbor Elf
Sakura-Tribe Elder
Wall of Roots
Repeal
Werebear
Krosan Restorer
Elvish Aberration
Step Through
Farseek