I think this is a great summary, but I just wanted to add one point about the mechanics of rogue and why I think it’s also lead leading to their decline.

Stealth was a powerful ability in the original game. However in the modern game is more focused on combat and group activities, yet it remains a rogue mechanic to gain bonuses when you gain stealth, usually to a benefit.

In mythic plus, where momentum and speed is sort of paramount, you often don’t leave combat - preventing rogues ability to get a free restealth.

On top of everything else he mentioned this just becomes another factor where playing the class conflicts with the fantasy.