Thoughts about Supergirl and Glee

You'd be partly correct. The key difference being is that SG is ending on its own terms rather than being summarily axed by the network. That is a huge bonus and a key win.

It isn't Melissa's (or the cast and crews) fault the show is ending, it's the nature of the world and the fans desires changing over time. The show began to lose its muster after the core EPs were let go (S2 and S3) and the replacements not being able to properly understand the character or thrust of the show, or to implement the needed changes successfully. To be fair, the have decent showrunners - but they're not suited for superhero shows.

Truth be told, the majority of the Berlantiverse superhero shows lose steam and creative direction after about 3 seasons. The fault is that the CW tends to automatically renew underperforming shows year-over-year, and by doing so lose a portion of the fan base due to poor writing, unfocused creative direction, and weak / uninspiring storylines.

It is in Melissa's interest to walk away from the project before burning out and becoming irrelevant even on her own show. Six seasons, especially for a female-led superhero show is a miracle. We'll take that for what it is deservedly worth. Melissa and Co. have done their time and it's in everyone's interest to move on to other things.

I actually felt that Season 4's problem was the New York storyline which took away from what made Glee a fun show...the high school aspect. What the shows have in common is that both went downhill after Ali Adler left them. Ryan Murphy's obsession with Lea Michelle killed the series. Had they used New York as a spinoff Season 4 could have fleshed out some great storylines.. and brought in new viewers.

As far as Supergirl another comparison is that it like Glee tried to service far too many characters. Big difference...Glee serviced Lea's character too much and Supergirl did not service Melissa's character enough.