My personal sign is when you start seeing awkward collaborations start cropping up. One time when I was thrifting, I picked up a graphic novel that had the Justice League, team with the Power Rangers of all things. I glimpsed into what the plot was about out of morbid curiosity and it was just a plain generic time and dimension thing.
Nothing ever connected between the teams at all. DC Comics, while fledgling at times with how they go about their series and movies, still have far more relevance than Power Rangers do. I think the Power Rangers are just grasping at straws to keep being relevant when people have largely moved on from them.
When the characters are talking about something and say “oh this is like that time when…” and a flashback scene which is just copy and pasted from old footage is used. Then they do this 5 more times in the episode. So annoying and cheap.
A clipshow episode. These were used as cheap fillers when the shows still had 20+ episode seasons, if the production needed to save money this was the easiest way to do it.
For all its other issues, Rick and Morty did this right. They had a clip show episode, but of things that had never aired. Others too, but Rick and Morty is the example that came to mind.