Long Live the Queen.
I was honestly okay with the ending. Given the state of the world and perhaps the limitations of what can be fed to and received by the audience at this time. What a tear-jerker. Honestly... I feel like writers, in their humanity, found themselves in too deep. Like to be able to write something so epic and ecstatic as what was to come when Magic flowed freely in Camelot.... was too much for the writers to handle or too much for the audience at this time to "handle" or both.

In addition, I think the actors were done. The interviews with the actors always speak of 5 seasons, 5 years, nobody as far as I knew confirmed a 6th season. Bradley James stated openly at the end he had been unhappy with the development (or lack thereof) his character and Gwen's and I think for good reasons. As diplomatic, polite, and classy as Angel has always been I could even see her going through the motions describing the unfortunately one dimensional state of her character for promotions toward the end. Or perhaps these are my personal feelings of frustration showing in my perception: I see so much more in Angel's Guinevere than perhaps was possible to publicly articulate for the masses (some awake, many not) at the time.

"Servant Gwen--->Queen Guinevere" was far more powerful as a Symbol than what the actress herself actually got to work with day to day, her screen time being so limited. At least in what I have watched of Bradley and Angel, they both seemed ready to move on. In contrast to the issue of her limited screen time, as a Symbol, the attention to detail given to her character was huge-- her deeply personal relationship with each of the Knights of Arthur's round table... having worked in Sir Leon's household as a child, sibling of Elyan, etc.... that gave each knight deeply personal reason to fight for her and protect her until the end, her social status arc, going essentially form 0mph to 100mph, servant to queen in one lifetime, her personality arc, going from bumbling and unconfident to regal and the epitome of self-realization... in just a few years. In contrast, Arthur the character seemed to make the same mistakes over and over and over again for much of the 5 seasons until the end and stay in the same dim mindset that so much of the plot stagnated around.

Symbolically it was well expressed by the series, that it was Queen Guinevere, a black woman, who would bring peace and freedom to Be to Camelot... upon Arthur's ascent beyond this Earth. In current society, there are few demographics that is more collectively oppressed than black women (apologies for the American-centric nature of that statistic... I imagine it is true in the UK too...) And her solitary sovereign reign throughout Camelot (metaphorical for heaven-on-earth, I believe) represents the prophesy for the future where one day the world "will be turned upside down" and the most oppressed will be revealed as having always been the most powerful of them All. Angel Coulby as Queen Guinevere succeeding Arthur's throne as the sole sovereign, she in and of herself is a symbol of the merging of the 5D and the 3D.. As above, So below.

I can only imagine that 1. the writers were overwhelmed at the idea of depicting that in a way that could be understood by the masses and 2. the collective audience, with that particular faction being so vocal about their hatred of the idea of a Black Queen who simultaneously contains both the energetics of the common folk and the One True Goddess Energy herself... the target audience became in direct discord with the message at this time. And this is why I believe in the ending as it was. As much as it does annoy me as well, that Aithusa's story got dropped like a rock into a pond, among other things.