I can't help but feel that every lane against an aggressive matchup is lost

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I don't often get that scaling feel. I'll be zoned out of my CS and they out cs me all the time. How can I scale better if he just has more gold? That's just a right out advantage for them.

All champions have different levels of power and are effected by items and levels differently. Generally speaking, champions who are very strong early on in lane don't grow as strong as fast as other champions for a variety of reasons. For example, panethon bullies the crap out of melee top laners, especially squishy ones, but he has to build squishy to do real damage and is short ranged compared to mages and adc who will eat him alive in teamfights later if he doesn't snowball like crazy. Additionally, at level 6 the ultimate pantheon gains is not useful in a duel, so any champion who DOES have a combat ult will have a huge powerspike compared to him. Imagine panethon laning vs darius and both are evenly matched at level 5 hypothetically. Then they hit 6 and both get ultimates... darius can now 100-0 panth if he uses his spells and ult but pantheon got nothing useful, hes about the same dueling power as he was at level 5.

That's an example with just two lane bullies but it illustrates the point pretty well - matches where you are weaker early tend to have a few tipping points where you start getting farther ahead by default just by staying even in gold. In many cases the curve is so steep that even being kills and cs and levels down is not enough to prevent 'scaling'. A jax or a tryndamere or a kayle or a ryze etc. will always start to get rediculusly strong after they get a few items, even compared to people who have more items than them. This is what it means to 'scale' - you accept that you are weaker early and play safe knowing that even with 2 levels down and half the cs of the enemy laner (extreme case) you will eventually catch up and surpass them in usefulness to your team. That toplane quin may get a few kills and push around your malphite early, but come mid and late game malphite is going to press his ult on the enemy carries and win the fight, and any items and levels he has in addition to that are just icing on the cake while quin dicks around trying to take a free tower here and there after her team is aced.