Certain spells need to have their mana costs updated

EDIT: THIS POST IS NOT ABOUT FIZZ. HE IS AN EXAMPLE CHAMPION. THE POST IS ABOUT OUTDATED MANA COSTS ON CERTAIN CHAMPIONS THAT HAVE NOT BEEN CHANGED AS THE GAME HAS PROGRESSED

so i've been playing a few champions recently who's mana costs on certain spells just seem disproportionately high. the best example i can give for this is Fizz's E. its his primary wave clear and csing ability, it's his highest damage dealing spell, it's the spell you max first... its his most important spell really, the defining spell of his entire kit. yet because of how high the mana cost is, he can only use it 2-3 times in trades or to avoid ganks before being completely out of mana during the laning phase or during objective contests

i've noticed mana cost changes to champions little by little over the course of the last few patches, sometimes you just make the spells cost the same mana at rank 1 as they do at each other rank so the cost doesnt scale out of control. sometimes you just make it a bit cheaper, like ahri's q, (i think its mana cost was reduced slightly recently, not 100% sure, but there are other examples of mana reductions). sometimes you remove the cost of a spell (like kayle ult)

my point is that most champions have had their mana costs balanced over time so that they can maintain a decent amount of mana in lane in case an all in or gank occurs, while still being able to effectively trade/harass or shove waves after they gain a few levels. but there are champions who haven't had their mana costs adjusted as the game has developed and evolved, and they really struggle in lane versus any of the ranged champs with very low mana costs that can harass endlessly while never having to worry about running oom

i know it is not as simple as just lowering/raising mana costs, it could be a combination of any number of things, such as

1. you could say that this is a matter of some champions having unusually high mana costs on certain spells (like fizz E)
2. you could say that this is a matter of ranged/mage champions mana costs being too low
3. you could say this was fine because every mid laner gets blue buff. but with blue buff lasting only 2 minutes now, and junglers needing their camps more and more in this new jungle so they dont fall behind, i think it's safe to say that riot doesn't "like" the fact that blue buff "HAS" to be donated to mid laners
4. you could say this is a matter of athenes / dorans ring / morello mana regen being too strong, and certain champions that cant effectively go these build paths are struggling because of it

either way, i was just curious if there has ever been a discussion about this between the balance team. would it be possible for you guys to take a day or two and just glance over every champion and their mana costs to look for any spells that seem like outliers or that seem outdated? do you think it's okay that ranged mages have such low mana costs and such high mana regen that they can shove every wave and constantly harass / spam their spells and not run oom? let me know! ; )