Do you feel Nexon exploits it's playerbase?

Well you can always not play if you don't enjoy it.

So lets assume nexon is exploiting us all? Who else is?

WoW? - I know people hate that this is brought up but it is perhaps the most well known MMO. They use the subscription system to exploit us. Clever devils.
Okay what next? The Car is dirty and someone offers to clean it. OMG EXPLOIT! He/She is using the fact that the car is dirty to gain money.
You need food to survive? The supermarket offers to give us food for a money? are they exploiting our hunger?

I could go on all day. Exploit isnt the word to describe this. But trying to get that accross is kinda impossible. lol

You're taking the nexon example, pulling out the bits that make your point fail, and coming up with new examples that fit in this broken idea you've come up with. Do you need to play maplestory? Do you need food to survive? Does your car stop working if you don't clean it? Do players that pay for WoW somehow differ from players who don't (besides you know... being able to play). Hopefully you see where I'm going.
Exploit specifically means it's an unfair method. It means they're using you. If you feel like becoming more knowledgeable on the subject, there's plenty of links online, including the ones I've posted above. Terms like "microtransactions exploitative", and "free to play exploitative" are good starting places.