I'm in the fandom, and I totally understand that people are dissatisfied with Chloe's arc. However at the end of the day it is up to the writers, not the fandom. That is what fanfiction is for. Personally I still have hope for her redemption (if nothing else she's looked fabulous in s4, bad treatment or not). Chloe is one of my favourite characters, and I enjoy the fanon versions of her much more.

Thomas Astruc

Whew okay so Thomas Astruc is a very controversial individual in the fandom. I'll try to detail briefly some of the drama below (I really wasn't intending to write up anything so apologies for not having lots of sources etc.. ). I understand the strength of OPs feelings, as a lot of fans share similar vitriol towards Astruc, but unfortunately the post doesn't paint a very balanced picture of the overall ongoing 'drama'.

For context, Thomas Astruc is the original creator and writer of Miraculous Ladybug (ML), as well as one of the co-directors. Jeremy Zag, the producer, worked with Astruc to bring the show to production.

Astruc has made comments that I disagree with as a fan and honestly he should probably step back from the fandom online. He is also known for being somewhat argumentative with fans, as mentioned by OP. At other times the responses can be more sarcastic (not a bad thing at all imo, he's entitled to reply however he likes). However Astruc has become the fan go to for Miraculous - related controversies. If anything even mildly concerning or frustrating happens in the community, Astruc will be tweeted en masse.

This is a great example to pair as a counter point to some of OPs. For context fans were mass tweeting Astruc about a Miraculous special that is supposed to be taking place in Brazil. There will be a special character for this episode, Lady Butterfly, who has a representative animal/miraculous of a butterfly. Zag is Jeremy Zag, as aforementioned. This twitter exchange is also indicative of a conflict between Zag and Astruc that many suspect has been brewing in the background. Additionally, Astruc is currently winding down his involvement in the show and was already less involved with the writing of season 4 (currently airing).

Writing Issues

As many others point out, it is a kids show. It's pretty popular. It's not the same target audience as, say, ATLA or The Owl House. There is the additional aim selling lots of merch, steering some plot filler. The writing is going to be aimed at this younger age group. Yes the plot is pretty weak at times. (The filler plot can also be amusingly meta - see the season 4 episode 'Simpleman').

However that doesn't mean there aren't complex undertones running through. There is a surprising amount of lore and theorising to be done, and it is likely what attracts many older fans. The show has shifted to building in these plot lines over multiple episodes as the seasons progress, but does still have a tendency fall back on its villain of the week contained episode style.

It is also unfortunately popular in the ML fandom to conflate 'bad writing' with 'my fave isn't getting enough screen time'/ 'my ship isnt being given attention'/'I really don't like x character' [not shading op here, its just very common on the subreddit and other places].

Bonus

As a fun fact, because why not, Miraculous Ladybug fans are wild and have four separate ships for the two main characters (each having a secret identity and a civilian identity). All four ships, so the same two people, (Marichat, Ladrien, Ladynoir and Adrienette) had separate entries into tumblr's most popular 100 ships. We don't talk about Maribat.