Before you react to the mana potion thing, consider the following...

So everyone is flipping their lid over the mention that Riot plans on removing mana potions. I've tried to have one rational discussion in a comment - without success - but thought I might be able to reach some people and have a calm debate about what this actually means.

First, what did Riot actually say?

Mana potions, on the other hand, are being removed. Our decision to remove mana pots goes along the same philosophy as starting items. 100 mana tends to benefit certain types of champions over others (with mana costs being balanced against individual champion kits) and can wildly shift from being a mediocre purchase to a very cost-efficient one. By removing mana pots, we can better balance champion ability costs with the mana regeneration stat while also streamlining the ‘sustain game’ of League.

Look at that last line, it is important. By removing mana pots, they can better balance ability costs & mana regen

This means that in the past when they're looking at mana costs, they have to consider that mana potions exist. A common concern I see brought up is Lux - she is notorious for being extremely mana hungry in her laning phase. Right now, they have to consider the fact that Lux can carry up to 500 mana around with her. By removing mana pots, they can ask the question, "What mana costs/regen is healthy for Lux?" instead of, "What mana costs/regen is healthy for Lux with anywhere from 0-5 mana potions." I'm not a designer but I have to imagine that plays a factor.

Then you have the mana efficiency they mentioned. At level 3 with 1 point in all abilities, Lux's rotation costs her 180 mana, almost 2 full potions. Syndra by comparison only uses 150. Vel'Koz, known for spamming his abilities, only 140. So if you consider mana potions as "How many spells am I getting out of this?" Lux gets less 'spells per bottle' than most other mages.

Further, it will hopefully allow them to properly adjust mana costs according to the needs of the Champion. That is, if a Champion is meant to be mana-gated early, but they can just circumvent this deliberate weakness by chugging potions, that is a problem. While mana potions come with some opportunity cost, they are pretty cheap. On the other hand, if the Champion is so starved that they have to invest in potions - yeah, that is a problem too because they're being forced to invest gold in consumable resources. Instead, they can evaluate each Champion and make meaningful decisions for each Champion.

Will it be perfect? Oh hell no. Is change scary? Sure.

But let's at least see what happens before we grab the torches and pitch forks. Angry indignation is more effective when we actually have data to support it.