Let's divide mages
So, lately there have been some discussion about mana, where we know,

was almost mandatory before its nerf, but now completely out-shined by

no matter what buff/nerf we do, there will be one item that considered better than other items, why? well because the differences between each champion in league are minimum, who the hell get more benefit in building mana over mana regen? ryze, I can't think another, maybe I missed some. But almost all the times it all just like "I am mage, I have to solve my mana problem, best item to solve it atm is morello, I'll buy it"
So how dividing mages can make no item become the singularity? dividing mages into two categories, giving them clear difference, will end up with different need of each.
I suggest we divide mages into
- Mage that has high mana pool;low mana regen Mages that concentrated to its poke ability fell into this category, we should adjust their mana and mana regen numbers. Giving them high mana, but to compensate with low mana regen. Mages in this category, focused on long term fight and to obtain the maximum damage, they should throwing spells with no rest. They will get more benefit in building Mana over mana regen.

2)Mage that has low mana pool;high mana regen Mages in this category focused in trades, or even all in, their mana pool should be enough for a whole combo or two, but they will oom after. To compensate it, they should regain mana faster. This mechanic is in between of first category and energy. Their high mana regen will make them getting more benefit in building % base mana regen.

And what about diversity? well, I think this is better than "I am mage and has to buy X", because now we have mage a,b,c,d that has to buy X, and mage p,q,r,s that has to buy Y. Mage in first category can buy seraph to give them totality in long term fight, or buy athene to give them 2nd category-y-ness. While you may want to tune mana regen items or making new one for diversity
suggestions are wellcomed
won't benfit a lot from a larger mana pool and just compounds the problem by making their mid games weaker until they get their item threshold and it will take them longer to get that threshold. It was also make it so that champs that need to burst can buy regen and largely be fine.
has spammable spells, but built in sustain, so instead he stacks mana over mana regen. Jayce has several spammable abilities, so he usually builds muramana, even though he usually wouldn't run out of mana if he built a regen item instead. etc.).