It's not really that surprising that there was never a whole lot of enthusiasm surrounding the movie. Nobody has even seen Carol Danvers in four years and she was barely even in Endgame to begin with. If we're being completely pragmatic, the only reason Captain Marvel did as well as it did is because it came out right after Infinity War and rode that hype train to the next station.
To be frank, we needed a Captain Marvel 2 movie in 2021 and we needed an Avengers movie by now that asserted Carol's position as the new Steve Rogers (aka the inspirational military figure). Maybe then Kamala Khan being such a huge Captain Marvel nerd would have made sense.
Iron Man came out in 2008 and we had an Avengers movie by 2012, a second Avengers movie in 2015 and then Infinity War in 2018 and Endgame in 2019. Endgame feels like it came out a lifetime ago and we still have no release date for the next Avengers movie and it's like they're skipping to the end too by going straight into a Kang's Dynasty and Secret Wars two-parter. That means we're missing two Avengers movies, or at least two big crossovers, that are the entire reason the MCU exists in the first place - to see these superheroes, who get their own franchises, team up with each other.
And that is a Marvel problem. Sony released Far From Home in 2019 and No Way Home in 2021 and both made an absolute killing at the box office. They probably would have released another Spidey movie this year if it hadn't been for Tom Holland wanting to take some time off and Marvel being so indecisive about what they're actually planning to do with the MCU right now. Sony already had to have super awkward marketing campaigns for the last two Spidey movies because they had to work around the MCU.