I must admit I was hesitant for a good while to write anything in the Entertainment section of the MB explicitly to express my feelings about this show.
It has nothing related to the message board itself but more of my often temperamental nature when it comes to things I love inexpressibly. (As in this case.)
So, the fact is that TDP not only became my favorite animated series on Netflix after I’d watched its first three seasons back in 2019, But it is, at the moment, has become my most beloved & adored show since Atla. 
Sure, it has a few minor writing issues, especially in the first season, but after that, it improves in miles with each step.
The 4th season did retain some of the less appreciated aspects of the 1st season, which is a bit unfortunate but understandable as S04 served as an introduction to the next Arc of the story (The mystery around Aaravos (the main antagonist).), so it’s forgivable, IMO.
The characters are all very intriguing and well-written, my favorites are still the story’s leading trio for various reasons I would like to explain in more detail, but I don’t have time for it now.
The world of Xadia also feels rich in myths and awe.
Overall, these are all I could write about this show.
If you haven’t seen it yet, give it a try!
It is worth it! 
Although I see where you’re coming from with these criticisms, I still feel that some of your points are not factually correct.
Well, except that a human mage used dark magic to turn the Dragon’s king Avizandum into stone thus waging war across the entire continent of Xadia. If I recall correctly, the prologue narration at the very beginning of the show mentioned that humans wanted dark magic because normally they couldn’t use “regular” magic. (or at least, most of them…) Plus, we did see in Viren’s case but once in Callum’s, how dark magic can corrupt a person’s mind and soul very easily.
-First, He’s not the main antagonist, that is Aaravos, the star-touched elf, who was prisoned into that mirror, that Viren found in his former friend, King Haarow’s room after He was assassinated.
-Second, no offense, but had we watched the same series? 
It was clear by the end of S01, that He was anything, but a good person.
He tried to kill His Best friend’s sons without any good reason, with His son and daughter.
Then, he tried to lead the other human kingdoms into a fatal war with the elves.
And last but not least, He tried to take over His friend’s kingdom from the rightful heir to the throne ( Prince Ezraan ) and almost turned that into a full-on dictatorship.
He is also incredibly smug, arrogant, and hypocritical towards anyone, who disagrees with him.
So, no.
He would’ve been a terrible protagonist. 
Breaking News! The trailer for the 5th season is here:
Edited for Triple Post - BioKnight