So what change to maplestory rustled your jimmies the most?

Potential was not bad when it first came out.
As long as we had the old damage cap, all potential did was allow the unfunded to reach it, by hunting for 3% or the insanely lucky 6% equipment drops from mobs. Cubing was only a shortcut.
When the damage cap was raised, though, and it suddenly became beneficial - and necessary, for certain bosses - to cube everything you have to Unique and 15%+, that's when the game became pay2win.

Yeah exactly. Potential as a concept isn't a bad idea. Plenty of games implement similar features. Diablo is all about a potential-type system in all of your gear. The problem is that it is nearly impossible to "happen upon" gear that was above Epic, and the fact that using cubes (IE Spending money) could permanently upgrade the tier of your gear made it a completely cash out system. The Legendary tier being added was Nexon just cashing in on it. They saw people bulk buying cubes and realized that they could extort them. Then they built the game around the higher end of this system, forcing you to pay or not be able to experience new content, which is the primary reason I quit.

The potential system had, for lack of a better word, potential.

The patch I most hated was Big Bang. It seriously made me want to quit.

I can never say that Big Bang was a bad patch in my opinion. It did some massive rebalancing that MapleStory desperately needed. MapleStory was a typical Korean MMO through and through for the time it was released. That means big grind for little reward. It was initially built around you spending days upon days to get a single level, and never seeing a drop worth your time. I remember playing for weeks in JMS to get Level 70, and that was with 2x EXP cards AND the 1.2x EXP boost that JMS had from its launch at the time. I spent weeks to get 70, and I felt like I didn't really accomplish anything. That had to change.

Additionally, there were so many areas they added that had literally no point. I remember being around when Ariant was added to the game. It added literally nothing of value. There was a new set of maps, new mobs...but in the end...everything was Level 30-40. It was pointless content. There were a hundred other areas of monsters that were better, with better spawn, etc.. It was useless. It had no point. There were tons of these areas in the game, and most content additions suffered this problem. I remember KFT and Omega Sector both also having this issue. When there was an area added with high level content, it had a different issue. I was around when Aqua Road was added to the game and it had a very low level section, and a very high level section, but absolutely no middle ground area. There was nothing for someone who wasn't strong enough to take on sharks, but too strong to bother with shrimps. There was no middle ground, no where to really grind, and no quests or anything to make me care about any particular area in the game.

Both of these issues were fixed with Big Bang. Sure, some people don't like how if the monster is level X, they always give Y experience, and I can't blame them, it's a valid complaint. There's several other valid complaints about Big Bang, as well. But compared to what existed back when I played before Big Bang? I'll take Big Bang, please. Not every change is positive, but the game was far better off than before Big Bang if you ignore the fact that the patch before Big Bang was the beginning of potential, and therefore the end. The core game was significantly improved. It's a shame that they then took potential and morphed it into the abomination that it is today.