Back in the day, we had [scryfall]Plague Rats[/scryfall]. That wasn’t a big card. Sure, everyone knew about it and probably everyone who had seen it had thought about using it, because we didn’t have the deckbuilding restrictions we have today. In 40 card deck with – say – 14 Swamps and 26 Rats (these days probably 15 or 16 lands and rest for the Rats), those could be pretty bad for you. We even had one of those decks as a gauntlet deck (a deck your deck has to be able to beat in order to be considered playable) for a while.
Over the years, they tried again. We had [scryfall]Pestilence Rats[/scryfall] which didn’t care only about others with a same name, but all rats. Then there were [scryfall]Relentless Rats[/scryfall] which was closer to the original [scryfall]Plague Rats[/scryfall], but partly by changing the rules on card limits. They are still reportedly pretty hard to get, because they are pretty popular in casual play.
Then, they finally got it right. [scryfall]Pack Rat[/scryfall] wasn’t taken very seriously year and a half ago, but over time they have become a format defining card after Kentaro Yamamoto played them in his Pro Theros monoblack devotion deck to a Top 8 finish over a year after the card first came out. Its actually such a format defining card that its beginning to lose popularity because everyone is expecting them and have weapons at the ready, including moving back to Esper.
From the other direction, there’s a debate on which is actually the best card in Magic: [scryfall]Black Lotus[/scryfall] or [scryfall]Ancestral Recall[/scryfall]. Each has been nerfed in a number of ways over the years.
Lotus became [scryfall]Lotus Petal[/scryfall] in Tempest, which still saw a lot of play and is also restricted in Vintage, Urza’s Saga brought [scryfall]Lotus Blossom[/scryfall], which has been pretty much forgotten, Mirrodin brought [scryfall]Gilded Lotus[/scryfall], which still enjoys a lot of popularity in Commander, and Time Spiral introduced the world to [scryfall]Lotus Bloom[/scryfall], which is an important part of some Modern combo decks, such as the current favorite based on [scryfall]Ad Nauseam[/scryfall].
[scryfall]Ancestral Recall[/scryfall] has a much more varied lineage, beginning with [scryfall]Brainstorm[/scryfall] which is still a Legacy staple and restricted in Vintage (and has its own family of nerfed offspring) and is even better than its ancestor in certain situations (such as against discard, where you can “hide” cards in your deck), to [scryfall]Ancestral Vision[/scryfall], which is banned in Modern, and beyond. Even [scryfall]Divination[/scryfall] sees some Standard play today in decks which are hungry for early land drops.
I guess the real interesting one is actually [scryfall]Lightning Bolt[/scryfall]. At first it was nerfed as [scryfall]Incinerate[/scryfall]. R&D apparently didn’t want to make a stictly inferior version at that point, but it soon became obvious, that they need breathing room with the card. After all, direct damage is red’s bread and butter, and red needs variety as much as other colors, so they decided to just make [scryfall]Shock[/scryfall] and be fine with it. These days we have [scryfall]Lightning Strike[/scryfall], which was a preceded by [scryfall]Searing Spear[/scryfall] and we are very fine with them. Still excellent cards. Many still play [scryfall]Shock[/scryfall]s and [scryfall]Magma Jet[/scryfall]s. And why not? They are pretty good, sometimes excellent, even though more situational then the original. Especially since there’s a big difference if you are trying to kill your opponent with them, which is why [scryfall]Lava Spike[/scryfall] and [scryfall]Rift Bolt[/scryfall] also see some play.
The thing about [scryfall]Lightning Bolt[/scryfall] is that its in a space where it will definitely skewer the environment where its available (people often play red in Modern and Legacy pretty much just to access it), but it isn’t backbreaking. It will certainly make weenie strategies worse, but its also pretty weak against midrange decks. To keep the environment dynamic, it has been reprinted every once in a while. It was last seen in M11. I wasn’t playing at the time, so I don’t really know how destructive it was. It was even in standard with [scryfall]Snapcaster Mage[/scryfall] for a while, so at least Development thought it was safe. It was also common, so it it wasn’t seen as too much for limited either.
For the development, cards like [scryfall]Lightning Bolt[/scryfall] and its ilk are an easy way to finetune the environment to go to a certain direction. For example, planeswalkers are very ubiquitous right now. Of the current fourteen Standard legal, I’ve seen all in one deck or another. Granted, two of them ([scryfall]Liliana of the Dark Realms[/scryfall] and [scryfall]Gideon, Champion of Justice[/scryfall]) I’ve only seen in my decks (and they worked great), but all the other ones have found places in decks, sometimes several and very different, like in the case of [scryfall]Jace, Architect of Thought[/scryfall]. This environment then needs answers to these. Bolt would work nicely, but since we don’t have that, we have been given some tools, such as evasion in many forms (although, strangely enough, we don’t really see much of flying right now), [scryfall]Fated Retribution[/scryfall], recently surged [scryfall]Dreadbore[/scryfall] and [scryfall]Hero’s Downfall[/scryfall].
So, getting things right isn’t so much about not doing powerful cards, but finding the right place to put them. Granted, [scryfall]Ancestral Recall[/scryfall] and [scryfall]Black Lotus[/scryfall] are too hard to balance to the environment, so they should never see the light of day again, but otherwise, there’s much room for tweaking power levels. I don’t think [scryfall]Voyage’s End[/scryfall] will be very popular outside of Theros limited, but in that context its an excellent card, often tantamount to straightup removal, if used on creatures such as [scryfall]Wingsteed Rider[/scryfall] after it has been targeted multiple times. Wizards understood this and thus didn’t just reflavor [scryfall]Unsummon[/scryfall], but instead made a card that costs one more, because that one is often very important in fast formats. People are gladly paying it and are even getting a bonus of scry. In a similar vein, [scryfall]Retraction Helix[/scryfall] seems almost strictly worse than [scryfall]Unsummon[/scryfall] (except that it isn’t because it can return any nonland permanent, but stay with me on this), except in this context where it can trigger heroic ([scryfall]Wavecrash Triton[/scryfall] or [scryfall]Triton Treasure Hunter[/scryfall] being very good targets) or it can be used to trigger inspired without exposing their creatures to combat ([scryfall]Pain Seer[/scryfall] being an excellent target if you don’t have too many expensive spells in your deck).
Seems to me like R&D now knows what they are doing. Sometimes some cards run wild for a while, but then they are contained by other cards as people become aware of them. After that they either go away, or stay but are not as powerful anymore. There are plenty of tools, you just need to find them (and there might not be tools for every deck…).
We should learn to trust development. As they seem to know what they are doing, we must evaluate cards in such a way that we can understand them in context. If everyone would rely on the old [scryfall]Unsummon[/scryfall] evaluation of [scryfall]Voyage’s End[/scryfall] and [scryfall]Retraction Helix[/scryfall], the Theros Block limited would look really different… and would be pretty awkward as there isn’t much removal and plenty of monstrous and heroic creatures.