It does rather feel like the lack of a chair for Dominique Thorne in the Doomsday announcement is a pretty bad sign for the storyline. Given that the show was filmed three years ago, Doomsday's writing team had full access to the Ironheart scripts, and maybe rough cuts of the show itself, so they could possibly claim they didn't include Riri because they weren't sure where the character would be at the end of this season...
I don't really see what that has to do with anything, first of all the series was still pretty far out, so the simply might have wanted to wait until the show came out to announce her being in Doomsday, and even if she's not that's not an absolute guarentee we won't see her again. As far as I know they haven't said that every active character will be in it, so there's still a chance she might show up somewhere else.
I finished up the series over the last week or two and I really enjoyed it. It's not one of my favorite Marvel shows, but it was good. Riri's storyline was a nice look at how grief can effect us, and the kind of choices it can lead us to make. Parker was a pretty decent villain, mainly because of Anthony Ramos performance. The big reveal that he was going after his dad's companies was added a nice bit of depth to his character.
I was a little disappointed the other members of Parker's crew just disappeared once he turned on them. After spending so much of the first half of the season with them, it would have been nice to find out what happened to them.
Zeke teaming up with Parker was a nice twist, and was a nice way to give us a more physical tech based bad guy for Riri to fight, but his storyline did feel a little anticlimatic.
After all of the tech and magic stuff being more or less separate, it was nice to finally get a story that brought them together the way this did. We kind of got a little of that in No Way Home, but at this level.
After fans kept expecting him to show up first in WandaVision then in Agatha All Along, it was nice o finally get Mephisto, and Sacha Baron Cohen was great in the role. He was a highlight of the series, and I really hope this isn't the last we've seen of him.
My biggest issue with this is one that's been building for a little while for me now, the lack of closure at end was annoying, since it sounds like this isn't doing well enough to get us a second season. First we got to big cliffhanger for The Eternals, then Moon Knight, and Agatha All Along gave us fairly open ending and it's getting annoying. I can see wanting to leave teases for a potential follow up, but it would be nice if they really gave us a good solid ending, with a little tease for a potential second season or movie, but the whole end of this felt like it was nothing but a set up for a second season that might not happen.