If you get a bad jungle, and the enemy gets a good jungle the game is over. The jungle can win every single lane by sitting and camping with 0 consequences. You don't get enough wards to cover all the places they can gank from, so you aren't allowed to even play the game if they sit near your lane, while the enemy is able to go full aggressive because they have the jungle with them.
Junglers can even can outlevel and out CS laners and some, like Lee sin, can straight up kill you in 1 rotation. If your champ doesn't have a million escapes built into their kit they just instantly die to any gank because immobile champs aren't given any tools/stats to survive ganks for whatever big brain reason. Riot also made this problem worse by killing jungle diversity and pushing farming and tank(and tanks in general) jungles out of the meta for good. This honestly is one of the biggest reasons this game is so frustrating.