This marco lore fits how I view devil fruit evolution in the series when it comes to the ancient kingdom.
The first fruits made were zoans, by copying animal lineage factor.
Next came low grade Paramecia fruits like the jacket fruit, weird crap like that.
Then we get into some good Zoans and Paramecias, and into low grade logias like the swamp and snow fruit.
Then we get into stuff like the ancient zoans, high grade Paramecias like law kidd and big mom's fruits and logias.
The final step in terms of the ancient kingdom, perfecting their science was creating mythical zoans, which were more or less gods and combined Zoan, Paramecia, and Logia properties.
This is why gear five luffy has Zoan strength, endurance, and regen, with Paramecia powers through stretching, and Logia powers through his flame based attacks.
Similarly kaido a mythical zoan has Dragon animal/zoan elements, a Paramecia like ability in Flame Clouds, and many elemental attacks like logia, including flaming torch dragon, where he pretty much becomes a dragon made out of flames hot as magma.
Mythical zones are the ultimate fruits, because they're combining Zoan, Paramecia, and Logia properties into a single unit