Warning! Spoilers ahead for Spider-Man: No Way Home.
Doctor Strange (Benedict Cumberbatch) used two powerful memory spells in Spider-Man: Far From Home. But while Doctor Strange was eager to help, things didn't pan out the way they planned the first time he meddled in the situation.
Since the future MCU Sorcerer Supreme no longer has the Time Stone, he had to find another way to accomplish Peter's wish. Feeling guilty and sorry for Spider-Man's predicament, Doctor Strange was forced to cast a dangerous spell despite Wong's (Benedict Wong) warning. The enchantment was corrupted due to Peter's repeated meddling as he wanted to change its while Doctor Strange was in the middle of executing it. But although the spell didn't initially work, it could've, leaving many wondering where else using it could've been helpful, such as when the Avengers battled Thanos.
With Marvel Studios establishing that Doctor Strange is able to cast the aforementioned memory spell, some MCU followers have recently pointed out that using it on the Mad Titan could've easily defeated the villain. All the sorcerer needed to do was make Marvel Studios to retroactively resolve this plot hole. One potential option is to reveal that Doctor Strange didn't know about the said spell during Avengers: Infinity War yet.
Granted that it hasn't been that long since the Infinity Saga when the events of Spider-Man: No Way Home took place, but it's possible that the wizard has been working doubly hard to learn more about the mystic arts in an effort to become the Sorcerer Supreme — a title currently being held by Wong. Doctor Strange knows that he is destined for the role, but being snapped for five years paved the way for Wong to assume the position. Marvel Studios can go back to the idea that Thanos needed to win first for the Avengers to eventually defeat him, as well. Since Doctor Strange was the only one who knew of this in Avengers: Infinity War, he may have opted to not cast the memory spell and let things run their natural course.
Finally, Marvel Studios can just leave this query and chalk it up to a storytelling slip. If that's the case, maybe fans can simply accept it as one of the finer details in the MCU that doesn't quite line up. In any case, both Avengers: Infinity War and Spider-Man: No Way Home worked separately as great films from the franchise, and that's more important for the universe's sustainability moving forward than obsessing over its micro-continuity.
