Big updates and the meta in LoL vs. M:tG

tl;dr: Of course games are going to be fast and snowbally in the pre-season. If you're a player you should try to be aware of if you're losing because something is broken or because you just don't know what's going on. If you're a dev you should be wary of if your change is going to overcorrect an outlier.

Magic: The Gathering's competitive Standard format receives regular updates to the game in the form of card expansions coupled with older cards being removed. This creates an expected shake-up to the meta as old decks need to be adjusted (or sometimes retired completely) and new decks enter with strategies that are not yet completely polished yet other players do not know how to deal with them, and it typically creates a pattern for what will win in the meta. This only really applies to immediately after the set release and it doesn't even capture what happens every time, but this is what happens more often than not in the immediate aftermath:

1. Aggro dominates - These strategies require little polish to pull off and win the game so fast that no other plan can get rolling.
2. Mid range dominates - Players figure out the best answers to the best aggro cards and pump out efficient threats that allow them to stabilize and win after aggro runs out of steam.
3. Control becomes viable and the meta starts to balance itself out - Once aggro decks start to become less common, the very slow decks have time to set up for big endgame win conditions. When they end up against the aggro decks the players have had time to figure out which aggro threats are really threatening to them and develop the answers to give them a chance, all while identifying which win conditions correctly evade the threats of the best mid range decks.

I think this has some parallels to Riot's pre-season and mid-season updates. On day 1 very few people are interested in trying out tanks with the new options and instead try to 1v9 with flashy assassins and skirmishers, players don't understand how much damage potential their enemies have and where that damage potential is so those assassins can snowball more often. Teamfights end in seconds since it's generally 5 squishies vs. 5 squishies and by day 2 the playerbase has declared it an Assassin meta. There are a few balance changes and the game's meta quietly shifts towards slower and slower strategies until we see nothing but protect-the-adc comps by the end of the cycle.

I think there is a bit of a problem League has that Magic does not: regular balance patches based on feedback. Card bannings and rule changes in Magic are very rare and only used against strategies that are considered very game-breaking. IMO this is mainly bad for Magic and only necessary simply due to the logistics: You can't change the text on a card to adjust its power a month into the cycle, general rule changes have drastic effects outside of just that one card, having the card do something other than what the text says is obviously a non-option, and a flat-out ban should obviously only be used in dire circumstances. However, the fact that League balances things regularly means that balance changes can get into a feedback loop where early game strategies that are only winning due to a meta shakeup get nerfed at the exact moment when players learn how to play against them, causing them to suddenly go from dominant to worthless.