Just so we're clear, over a year later, no, the mainstream did not like the ending to the show. The finale was the lowest rated episode in the show's run outside the first three episodes which was a slow build.
https://www.ratingraph.com/tv-shows/wandavision-ratings-85403/
Time hasn't been kind-- short as it's been. It's already slid 0.3 points since it ended last year. With that rating, on IMDb, it's only the #23 ranked English-language non-documentary TV series or Miniseries that released in 2021 with over 5K total votes.
It ruined most of the potential it had going with that high we got in Episode 5. Could have been a Top 3 show for the year. At least it partly justified its ending as Wanda turned out to be a villain, indeed, in the extended MCU, as she was the primary antagonist of the latest Doctor Strange movie. However, that doesn't justify the cartoonish treatment of the so-called villain of
Wandavision itself. As I said last year, in this thread, the show could have been good if it centered its disruption of expectation around making Director Hayward of SWORD the good guy.
Wanna see great TV from 2021 about powered heroes and villains? Watch
Arcane.