A very useful plugin for any server owner looking to create interesting and unique mobs. However, the plugin isn't simple and comes with a large learning curve for anyone new to using it. I suggest being very patient with the capabilities of the plugin as any small error can break your mob or item(if you choose to buy and use the artifacts add on).
If you use the mythic mobs extension add on, please know the plugin was made by another individual and not by the author of the Mythic Mobs plugin.
Keep in mind, although the free version is "old", it's at least stable to use. The author is not demanding anyone to purchase the premium or development builds, they are only additional options for the owners to choose from. I would also like everyone who's interested in those options, look at the fine print of each option's description in order to make a wise decision, since money is involved. One more thing, there is no pay wall to download the free version of the plugin. If you don't believe me, click the download button and click "MythicMobs FREE VERSION" or just visit the bukkit page:
https://dev.bukkit.org/projects/mythicmobs
I have used this plugin for over two years, yet I'm still learning new aspects of the plugin because this tool has many possibilities in customization. Here's a mob I created using Mythic Mobs:
https://streamable.com/x2mzn
For anyone with complaints about support, most people who provide help are just users of the plugin like you or me. The ones with specialized roles on discord or the forums are usually just very active users of the plugin. Please don't yell or insult the very people trying to give advice for what may seem to be a very specialized problem. For those who were left with a bitter taste, the author has many other priorities in life and can't dedicate a full 24/7 to the plugin.
In short, Mythic Mobs requires patience, persistence, determination, dedication, and creative thinking to bring out the full potential the plugin has to offer. I hope any new user who view this, may understand.