I hope posts in English are welcome!
I watched the season 3 and I really loved first 2/3 parts (Japan and India) and felt very dissapointed in last 1/3 (Arabia). At the beggining I was watching the show and thinking "season 2 wasn't bad, but THIS IS SO GOOD", I wished Mysterious Cities of Gold will get as popular as Miraculous Ladybug around the world thanks to season 3. It wasn't perfectly like season 1 (still my absolute favourite), but was just so, so good. Characters were closer to their orginal personalities (minus Zia), episode where our heroes discovered that Zares is Ambrosius was perfection, India episodes was something really diffferent and refreshing. There is not many adventure shows or movies right now and MCoG3 perfectly fit the niche.
And then Arabia happened. Zia powers started to grow stronger and stronger and her calm, quiet personality was totally gone. The idea that Mendoza, Sancho and Pedro would like to go back to Spain after they recieved gems was really stupid. They wanted gold, at the first place and after they went back to Spain in season 2 they were prisoned. And they left children completly without help of any adult and they thought that Ambrosius and his team are stopped after being surrounded by carpets.
They even didn't take Ambrosius' compas or find Nef and broke flying mechanism. It was far, far worse that Esteban singing that annoying song in episode 12 of season 2. Later Mendoza acted really OOC at times, he is supposed to be clever tactician and adventurer with common sense, but he was doing really stupid things like stealing the camels or leaving children without anybody. Tao and Esteban were really sidelined and Zia was the main star and she was so... unlike Zia. She was attacking enemies, she was first to fight or run somewhere, she was solving puzzles like a boss, she was loud, tomboyish and over-powered. She was nothing like Zia I know and really like (my favourite character after Mendoza). Season 2 make a good job in giving Zia more important role, more action, but still being close to her orginal character. I also don't see why they made Zia tomboyis action girl when theu introduced Laguerra - new character that is a woman fighter. Why we don't have one calm female character and one that is brave, good at fighting etc. but instead the made both a bit similar in role (action girls stealing show from rest of characters in last arc)? That would be more diverse.
I also really dislike Isabella/Mendoza pairing in a way they were presented in show. I hoped that they would be rivals and Laguerra would be an enemy that maybe will change sides in next season after realizing that uncle Ambrosius is more and more crazy. But they went for romance instead, sigh... I think that kiss scene in last episode was terrible and so unrealistic/stupid act from two intelligent characters. Children were going to die, City is destroyed!
I have nothing against adding romance to the show or Mendoza having love interest. But I don't like that his love interest was basically a female copy of him in many aspects. Good at fighting, caring about children but beiing ambigous (good thing is that they were ambigous in different ways),winning fights in clever way, Spanish, quite charismatic. For me it feels like they try to replace Mendoza and I just don't like the idea "make lovers so similar to each other".
I also loved the character concept of princess Rana Ori and I wished they told us more about her! They should be in the city for two episodes and maybe watching holograms telling a story about Rana's life? It's her tomb after all. And city was beauttiful.
So, for me the first two arcs were really, really good! I wwas repeating "SO GOOD" quite often while watching. I loved it, it was worth waiting 3 years, I felt they learned a lot from mistakes of season 2. I just loved it.
And thir arc destroyed this season for me and I'm not waiting for last season with big enthusiasm like for season 3. It's sad that my favourite character's personalities (Zia and Mendoza) was really destroyed/changed in this arc. The most triggering moment was probably that kiss scene (UGH).
There is a few really good things in Arabia episodes (egigmas and City of Gold desings, beduins culture, Ambrosius becaming really powerful villian), but there is more things I don't like.
So, my ranking of seasons:
1. Orginal/First season
2. First 2/3 of season 3
3. season 2
4. last 1/3 of season 3
Sorry for all mistakes in English. Neither French or English is my first language.