It is perfectly understandable, at the beginning I barely knew how to sprite. My main goal with this is to make shiny sprites of the highest quality possible.
About Exeggutor, I intended to make it look as much as a coconut tree as possible without maling the torso and heads being too similar, but it couldn't be too different from the original that way. That being said, I'll look into it and differentiate it a bit more.
Homerbro just seemed hilarious to me, but I can give it another shot, to make it slightly more original.
Might Gai's take on Electabuzz is already great, in my opinipn, so I believe you should go with that.
For Voltorb and Electrode I aimed to make them look like the overworld TM icons, as the idea of making them look like pokeballs didn't seem that original to me. I can give it another shot tho.
I'll also fix the Blue Birds group as soon as I can.