Wow, I enjoyed reading your take on the episodes and comparisons to similar issues I have encountered several times from the fandom since G5's airing.
FYI- I'm going to go a bit off tangent at times as I have so many thoughts.
I'm sorry to hear that you have been insulted by others who claim to be a part of this fandom. I have been told to "go kys" and other horrible things before by "G4 purists" who cannot accept anything that isn't G4 or any valid criticism, however they feel like they can nitpick the tiniest things from G5 and basically make it their premise of hate. I don't mind if someone has a different opinion and has valid criticism, but if they start insulting me from the start and aren't willing to hear a different opinion, I realized that I cannot have a healthy discussion with those people.
I felt MYM had a great batch of episodes where the writers explored several ideas introduced back in FiM and tried to improve upon them. It was refreshing to watch. I thought they did a great job with Misty's arc. You mentioned redemption arcs and I understand that some people do not like the redemption of a villain trope, but I liked the notion that they tried to attempt it for Starlight. Some people don't believe in second chances or that by forgiving these characters somehow means that we're okay with all their previous heinous actions, but that is not the case or the idea at all. For all these redemption stories, the idea is to look further beyond that as person. It sounds crazy to some, but people can change and everyone changes in different ways as we all grow in different ways. Some can argue that things could have been executed better and more, but these situations are never perfect. The examples you provided regarding Nebula, Tempest Shadow, Princess Luna, and Lilith sound like nice exceptions at first, however when examined further- they have all done some terrible things that people would never forgive, but they were forgiven just like Starlight. It's purely subjective and there will always be some form of scrutiny from fans. Hell, I remember seeing arguments from people who thought Luz should have tried to redeem Belos! I give Dana Terrance props for doing something different for an animated kids show.
I do agree to an extent that some people are projecting their own personal issues and want to impose all these negative and toxic behaviors from these adult shows to kids shows as well. I have seen IRL and in shows where friends and couples have trashed each other as well. They would seemingly classify it as "normal behavior", which is sad to see. I'm glad G5 is doing something different and portraying healthier relationships between characters.
As much as I loved G4, I think that those later 4-5 seasons felt like a chore to watch at times. G5 generally doesn't feel that way for me. Sure, FiM had some fun little moments sprinkled here and there, but it wasn't the same show I came to love in the first few seasons. It doesn't mean I hated them, it's just that I found that the consistency of quality fell through after season 3. I was surprised to see that the G4 purists overlook all that stuff due to nostalgia, but nitpick the smallest thing they don't like about G5. I recall seeing a while back that some people were trying to compare the best episodes of the entire G4 franchise to only the best episodes of Tell Your Tale. I have met people who act like MYM does not exist because, and I quote, "it is 3D/CGI and therefore does not count as a series".
In my opinion, the reality is that G5 has "caught" up to G4 in terms of general quality when you examine the entire plethora of series so far. It's just that a certain group of think that anything that is a sequel must be 100% better in every way or it's considered a complete flop and in this case, it's not. Every series has its ups and downs.
Some people may not agree with that and other opinions I expressed here- and I'm okay with it. There are plenty of valid criticisms where G4 and G5 have plenty of issues, but they are still wonderful in their own ways. There are some passionate fans here who see that and I'm thankful for them. Unfortunately, there are other people who do not want to give any credit where credit is due.