I keep reading comments that misinterpret Wanda's turn in the movie; Wanda didn't turn evil she was corrupted by the Darkhold and that was established in the film many times; Illuminati Strange was aware of the dangers and had to be killed, we then had a fight between 616 Strange and a corrupted Strange.
Sure her actions were atrocious but wasn't really different than Bucky/Winter Soldier or Hawkeye under Loki controls or even Loki! They received redemption and a 2nd chance.
Wanda has become my favorite character in the MCU. She has such a tragic story - her parents were killed, she joined rebel groups and was then experimented and manipulated by Hydra; her brother died, as soon as she found a family in the Avengers she was deemed a threat by the government, got imprisioned, was on the run and had to kill the love of her life only for Thanos to undo it and kill him again; unbeknownst to her she created a reality where she had a family but was also controlled by Agatha and had to give that up.
She's the strongest being but with a weak psyche due to her grief and loss and that makes her susceptible and easy to manipulate.
The inclusion of Profesor X served many purposes. It introduced the concept of the X Men and Mutants, to represent a member of these groups (X Men, F4, Inhumans) in one scene together for the 1st time in cinema, to pay tribute to the actor and show Wanda strength.
The always optimistic and hopeful Profesor Xavier was there to help guide Strange. Just because these other Stranges were going down a certain path he didnt have to follow, he could trust others so he wouldn't have to be the one holding the knife and become a different Doctor Strange.
Tl;dr
The line - "Just because someone stumbles and loses their path, doesn't mean they're lost forever." Was as important for Doctor Strange as it was for Wanda's. The same sentiment carries over to Wanda and we saw in the end how she tried to redem herself for her mistakes and seemingly sacrificed herself and destroyed the Darkhold accross universes so she and others wouldn't be tempted.
Just because The Darkhold prophesied about her ruling or destroying realities she had to follow through, just because she fell and lost her path while corrupted does it mean she is lost forever and she too could be a different Scarlet Witch.
Those saying the Illuminati served no purpose missed out or overlooked the importance of the line in the context of the film. Dare I say it was as important as the great power line in NWH.
I disagree with your characterisation of Wanda and her descent.
In WandaVision, Wanda enslaved and tortured an entire town full of people because she couldnt deal with grief....before she got the Darkhold.
She
chose to use the Darkhold. No one forced her to utilise its power.
No doubt it corrupted her further, but she was already willing to do evil things for selfish ends.
Sure her actions were atrocious but wasn't really different than Bucky/Winter Soldier or Hawkeye under Loki controls or even Loki! They received redemption and a 2nd chance.
There is a clear distinction between her conscious choice to use Darkhold and the actions of Bucky and Hawkeye who were both under the control of other people and had no ability to make their own decisions. Their actions were not selfish or even evil...because they weren't making conscious decisions.
You could argue that the Darkhold corrupted her, or maybe had some control over her. But such an argument is weakened by the difference between her use of the Darkhold and Dr Strange's.
Wanda uses it to possess other versions of herself and commit mass murder, in her pursuit of America Chavez's power.
Strange uses the Darkhold to possess another version of himself to try to stop Wanda from murdering America, taking her power and going on to do other evil deeds.
Wanda's aim is a selfish one, Strange is motivated by the greater good.
Were her actions different from Loki's ? Well, both were party to mass murder - although Wanda more directly as she killed a lot of people personally, while Loki led the Chitauri invasion.
Was Loki redeemed ? I'm honestly not sure. For every time he helped Thor or did something morally good, he also seemed to do something selfish or evil. Thanos found the Asgardians and slaughtered them because Loki had grabbed the tessaract/space stone. Did he know that would bring Thanos down on them ? Unclear, although Loki did work for Thanos. Who can say for sure?
I'm only referring to the movie version of Loki, not the Loki from his series - but if you think that series redeemed him, I won't argue with you, because I honestly don't know.
So who's worse Loki or Wanda ? Well, Wanda posed a threat to the entire multiverse, according to Wong.
Was Wanda redeemed? Well destroying the Darkhold is a pretty big deal. How does that weigh up against all of her murders and the whole Westfirld thing ? Honestly I don't know. For me, she's still a villain.
Don't get me wrong, I understand why you like Wanda as a character - because she's a great character, but to me she ends her life ( assuming she's dead, and that's probably very unlikely) as a villain. She does terrible things for selfish reasons, and uses her grief to justify her actions.
I thought Elisabeth Olson did a great job, despite terrible material, to make Wanda compelling.
It was a very strong performance - and a few times outshined Cumberbatch. Have to say I loved watching her massacre the Illuminati. I have tons of problems with the writing of that scene ( like why didn't she just crush Captain Carter like a bug, the way she crushed Thanos in Endgame? Why bother killing her with her shield?) but not at all with seeing Wanda take them all out.
I wish Wanda had owned her villain turn - she could have been the next Thanos.