I'm glad you liked the animation! I've thought about showing different POV bubbles. The one idea that I'm excited to try at some point is an egg cell being assaulted by sperm cells so you can see the impregnation process. It'll probably be something we'll see for the Ending scene with the King Hornet.
So my thought process behind the Slime is that they are common enemies in every level. Each level will have a different base color and weapon. My reason behind is due to the simplicity of their design. I literally drew, colored, and animated it within 2 hours or less. I can easily mass produce them and have them fill every level to save time. You can see the abundance of slime sex scenes if I did make one with each grunt with the different adventurers.
Not to worry, I do plan on having a Slime sex scene and that'll be with a Giant Boss Slime. The possible sex scenes with Slimes are nearly endless.