1) Lack of free time, combined with procrastination and not portioning my time correctly.
2) Having never used MZ and thinking it would be like MV. It is, but the plugins are a bit different and I never figured out how to use most of them correctly.
3) Lack of resources/assets. I tried to use RTP, but a lot of the characters I wanted to use were missing either sv-battler or sv-enemy graphics. I tried making some characters in the generator but that was also pretty limited.
It's weird, but I had a ridiculous amount of trouble trying to get plugins to work. I bought MZ specifically bc it handles plugins better than MV does. But I had a hard time figuring out the Help files for a lot of the plugins, I couldn't copy commands out of the Help files (unless I wanted to open the actual file up and copy from there), and a lot of times things just didn't work the way they "should." I wasted a lot of time trying to do things that never worked.