It gets worse as the game progresses because of the scaling death timers. You can die in first blood and still come back for the first wave, but after 5 minutes you will start getting behind In levels. That's why its always good to understand this rule of thumb for league:
AP casters are typically early to mid game, some do scale well into late (
for future reference I refer to him and the like as AP CARRIES). These will suffer more if they die early, and if the tables are turned will give you the hardest time early game (aram)
AD casters are the same way as AP castors, but their early game is worse and end game is better because they are often bruisers, fighters, assassins.
For example is a jugg, her early game is very mediocre but she has a big powerspike at 6 that continues until she hits atleast level 17 where she tends to fall off unless shes building heavy tank items.
Tanks are mid to end game monsters since they don't rely on damage to be reliable and useful. Theyre typically very squishy early but if they get to turtle for as long as they can you will understand the hidden power of tanks after the 14-15 minute mark (aram, aka warmogs).
ADCs and hypercarries are "weak" early, but after they get one tier-3 item your best bet is to focus them every chance you get. Theyre going to be the prime reason for your wins or losses in aram. These are the ones tanks fear the most and the assassins/AP casters or carries want to explode immediately.
APCs are just like ADCs except they do fall off late instead of being weak early and are muchhhhhh weaker vs melee champs that build hp and/or mr. However you can crush ADCs with impunity.