Just why do League have so insanely long seasons?

I hate this and it doesn't make sense for me. Those who want to get Gold can practically play just 10 games and then stay AFK, meanwhile Challengers have to spam a stupid amount of games unless they start their grind very late. Even diamonds are allowed to ignore the game for a month, meaning they need to play max 10 games more once they have reached that tier. Gosh...

Is the system designed to give time for hardstuck silvers or what?

Think about this: the final days of ranked have been in November last seasons, and Riot have always put Gragas to his weakest state before worlds, so it's actually pretty dumb forcing me to play the crucial games that time rofl :D