The fate of the Kingslayer...

This is what every fool and his dog believes so this is what will not happen.

This show both foreshadows and misdirects.
Characters barely ever get to do what they say they would, so Arya will not tick off all names from her list, Daenerys will not take the throne, Euron will not marry Cersei…

Real foreshadowing comes only once and there have been two very explicit cases of a strong announcement never repeated, which I believe will come true for this very reason. Both were in S3: Melisandre telling Arya they would meet again and Jojen telling Sam armies can't stop White Walkers. These two things went so completely off the radar they must be waiting for a surprising "told you so" sort of return.

There's a third one about Jaime. When discussing death in S5, he was made to tell Bronn he wished to die "in the arms of the woman he loves".

Jaime killing Cersei is rooted in the "valonqar" theory. It is book-only in that it stems from the end of the prophecy Cersei believes in, in which she was told the "valonqar" (Valyrian for little brother), would "choke the life out of her".
In the books, Cersei has mad dreams about Tyrion, her little brother, turning up in her bedroom to kill her, which is why she sets a price on his head and it explains her irrational feelings towards him. The whole thing is meant to show how "prophecies" get people who believe in them to act in otherwise unexplainable ways. It must be added that Myrcella was not killed in Dorne, only hurt and Tommen is still alive in the books, which end before Cersei's trial.

Enter the small detail stating that Cersei was born first, making Jaime her other "little brother". Some go on to spin theories that someone else's little brother, not Cersei's, will kill her: The Hound, Theon, Euron, basically whoever had an older sibling, even Arya on the assumption the Valyrian word would be gender neutral. They are thoroughly missing the simple point the author wants to make: "people who believe in crap do stupid things". He's made that point with Stannis too.

The show left all that out. The "prophecy" of the resentful "witch" ends without that part so we can believe it will have no impact on the story. There are those, of course, who say it was left out to keep it as a surprise but it isn't one because it has been discussed to death by book readers. The show runners have exploited this by giving Jaime that ambiguous look at Cersei at her coronation. It made people talk and they love to stick a middle finger in the face of book purists. Another example of this in S6 was to have The Hound take a piss in the river. In case you wondered, that sight was not fully gratuitous.

So there you have it, Jaime killing Cersei comes from the rambling of fools.

All we know is that something resurrects people. It does not give the forced prediction of some wood witch any value nor does it confirm the nonsense Melisandre had Stannis believe. She was wrong and it led to disaster, even if the "Lord of Light" or something else is real.

Character's psychology is always explained by some of their past. It can be a flashback sequence or something someone says. Cersei telling Ned she wanted to love Robert at first was the same kind of thing. Jon telling Sam about not wanting to father a bastard, Stannis telling Davos how he was left aside after the rebellion worked the same way.

In the books, the Brotherhood Without Banners comes upon the dead body of an important character floating down the river. Beric Dondarrion sacrifices himself to have this character brought back which becomes known as Lady Stoneheart. This character was left out of the show, to the great dismay of many book readers and every coming season saw people theorising about how it would still happen, then expressing utter disappointment that it didn't. When the Brotherhood returned in S6 and sat by the river while the Hound was taking a piss in it, it was a direct "fuck you" to the purists who had been trashing the show for leaving out their favourite zombie thing.

who?? jamie? jamie and gilly??? like together ? how and why?

A point can be made that the story keeps getting worse as it goes along, and I mean the book original, not just the TV show.
It gets cheaper, dirtier, crazier and more horrific after the third book and this is where Cersei going mad and stupid takes place (the original book character is a joke, nothing like the show). I have been calling the author a pig and a fat wanker for a reason. I think he's a baseball fan too.

That prediction is the reason Cersei goes against Margaery, though, and that could not be removed. There had to be an irrational motive for an otherwise intelligent character to go against her most powerful ally. The alternative solution to this would have been to make the Tyrells more aggressive but they were to remain the "good guys" victimised by the "bad" Lannister queen, I'm afraid.

The anti-religious bias is blatantly typical of the completely left-driven entertainment industry. Westeros is their portrayal of a modern society in medieval looking costumes.

As a complement to this, here is an aside I posted to the old IMDb forum back in May 2016:

I have liked the show until S5, forgiving its shortcomings for the sake of the intrigue and the discussion potential it offered. My first posts were in defence of Tywin Lannister.
I hated S6 and never watched S7.