Fix summoning system, the big one is reworking how the pity rate works
When your gacha game actively *punishes* you for pulling an off-focus 5-star, you know your system is flawed
There are different solutions to this problem but SOMETHING has to be done.
Add more bonus units to arena and AR
With the massive cast in the game, 10 units is simply too low. This is especially true in AR where there are units in the bonus pool who literally cannot be used in certain seasons so you're sometimes working with only 8 bonus units.
At least 15 units bonus, and the 5 extra units added should be either units that were Thanos snapped away earlier this year, or they're from the 3-4 star or grail pool.
Do something regarding fortress levels in AR
The drip-feed pace of aether stones means that newbies are hard gated by fortress levels and it is often impossible for them to climb past a certain point because of fortress.
There are different solutions to handling this problem but SOMETHING has to be done.
There are also plenty of small fixes they can do to existing game modes, such as actually improving the training tower, and other QoL or UI stuff such as adding more value to friends list.
You can't spell Salt without Alt - Poison-puffs