I always get frustrated when I see newfags on /mlp/ flagrantly exposing their newfaggotry under the guise of larping about "Muh BOARD CULTURE".
You're all spot-on that /mlp/'s original board culture died a long, long time ago. All you have to do is spend a half hour or less on desuarchive combing through threads and posts of the golden era to see how radically different the thoughts and attitudes, likes and dislikes etc of anons were compared to now.
As a forlorn soul who has been through it all, /mlp/ specifically has gone through the following ages, each with their own dominant board culture of the time.
The Golden Era:
The original, true spirit of /mlp/ that existed from the boards creation onward, until...
Prompt Ban/Glimmertard Era:
Arguably the single most damaging event to /mlp/, the effects of which are still being felt. During these years, creativity and content creation were stifled, the userbase was bled and drastically reduced, and a shift towards hating the long-established things and tropes that /mlp/ loved began to take root.
Additionally, a dedicated troll presence was established. I would bet money that the exact same group of people who were responsible for filling the catalog with dozens of Glimmer threads, day in and day out for years, are the exact same ones responsible for EqG trolling and G5 spam.
2016 Election Tourism:
Overlaps with the prompt ban era, but I think it's worth mentioning on its own. 2016 itself was a year that changed the internet as a whole, and it hasn't been the same since there. 4chan(and other imageboards) were particularly effected by this shift, no matter the board.
Post-Prompt Ban Era:
Too little, too late. There was a definite improvement in board quality, but by the time the ban lifted, /mlp/'s old board culture and userbase was already decimated.
And finally, we arrive at the most recent development; arguably the worst and most damaging one since the prompt ban.
Post-Town Hall Era:
The sudden drop in quality >>10567
mentions is the direct result of this. Hell, it's why this site was even made. That shitty event of Twimods did nothing but expose the true intents of the 4chan moderation team to a wider audience, while also formally legalizing and giving a green light for trolls to do their business. Blatant EqG trolling skyrocketed from this point onward.
That's my interpretation of things, anyway.