Custom animation adder for Java entity models

I don't want to use the Geckolib plugin at all. Because walking speed, waiting time for animation repetition, etc. very inconsistent. But my biggest complaint about geckolib is that I cannot make my mod work on its own without needing a plugin. Blockbench has a plugin called "Animation to Java Converter". This plugin adds animation tab for Modded Entity in blockbench. Also I can't use animation keyframes in geckolib. Geckolib only supports linear keyframes, which transition very sharply. And admit it, this looks really ugly. Below is the link to the photos where I show what I mean.

https://photos.app.goo.gl/Ve4p1U8xY1CxQwLH8