I dunno, I watched the whole of Cursed, so we certainly found it “watchable”. The acting and writing are generally fine - the dialogue is actually better than, say most The Witcher (which is a low bar, but I didn’t hear a lot of dialogue-based criticism of it). The plot is more questionable, but it has its moments. Like I said, though, it takes a while to gel into anything at all.
Sure, though again different setups will make things look more/less artificial, as per my example with GoT. I don’t think you’re going to do much better than GoT with sets/lighting, but people managed to make that look completely fake with the “right” settings.
40K is more vulnerable to this because it can’t even use real places for most sets. Cursed has a huge amount of location shooting, so it’s more the set-dressing that’s an issue, whereas 40K needs to create sets out of whole cloth, as it were, which is harder.
40K does have the advantage that once the sets exist, they can shoot on-set instead of on-location though. But this can sometimes turn into a disadvantage (c.f. Altered Carbon S2) if they simply decide to cut your budget because you already have sets, and force you to reuse them.
It’s entirely Excalibur’s fault.
Once you’ve done it “right” like Excalibur did, there’s zero mileage in traveling that road again. Morte has tons of material but I don’t think it would be anywhere as easy as you’re suggesting to make a good series out of it. You’d have to make up or expand a lot of characters, whilst probably combining others, at which point people like you are going to accuse them of “fucking up the Arthurian cycle”, because they didn’t focus on the thing that person felt was important.
This is the problem though, who determines what is “extraneous”? What is essential?
You’ll never please mythology nerds, because even they all have entirely contradictory opinions on which bits are “essential” or “extraneous”. Is Achilles invulnerable or not, for example? It’s not in the Iliad, but it’s a very prevalent approach to him, and you’ll piss people off either way. Or pretty much any approach to Hercules - if you pick one source and pare it down, people are going to go “WTF!?!?!” about “missing” stuff (indeed that’ll go beyond the mythology nerds). You yourself mention Lancelot.
And how many of the odd connections between mythologies do you use? For example, in some Norse myth, Memnon from Trojan myth is Thor’s father. Memnon is, as you may recall, a black guy - an Aethopian prince (like definitely properly black African, no question about it). Be interesting to see the first take on Norse myth that has the balls to make Thor, a figure literally worshipped by some white supremacists, mixed-race (even though it makes complete sense based on that mythology).