>>532505532
Early game pressure leading into lategame utility. Mages spiked the hardest of any class early (level 6 power spike was insane on champions like Annie, Veigar, Twisted Fate), tanks did better midgame once they got 1-3 items, and eventually ADs would take over lategame once they finished their core of IE/PD/BT/LW. Mage damage tended to fall off lategame, cooldowns and manacosts were higher, and waveclear and objective control were weaker compared to ADs. This is back when baron was a threat and towers didn't die in half a second to a coordinated push.
Defensive items like GA, Randuins, Bveil, Frozen Mallet were also strong enough and perfectly acceptable to buy on anyone, and the omnipresence of Aegis of the Legion meant that every team was getting a significant boost to survivability. Because of this, it was acknowledged that after you took advantage of your early game power as a mage to get your team ahead, you would transition into CC machines, the most obvious being Annie's AoE stuns and TF's global pressure with gold card ganks.
It's also why assassins, which weren't super common back then, were balanced around having silences. You'll see a lot of clickbait youtube channels and retarded zoomers constantly parrot "OH MY GOD TALON HAD A SILENCE????" Of course he did, because it was a way for Talon and Kass and Leblanc to function lategame without making them just oneshot everybody at every stage of the game. Unfortunately pic related happened in season 3 and ruined the game.

>>715039286
While season 5 looks like a godsend compared to modern league, never forget that the decline started in season 3. That's when esports went from "oh we'll support them because people want to be competitive" into "we're now focusing on esports as our primary design philosophy". This meant speeding up gold generation, reducing cooldowns across the board, nerfing tank items across the board, increasing damage across the board, and having to find a way to make tanks good again so fuck it just give every tank more damage that scales off HP or tank stats, oops tank meta guess we need to add more damage...a never-ending cycle.

Yes, season 3 was still "good" because it was coming off the backs of old League. But it was one of the first stepping stones into the eventual decline of league into nothing but nonstop ability spam with mobility and damage creep out the ass.