General tip - don't make a point and then get defensive when people assume that you meant the exact words you said. Nobody here is a mind reader, if you want to make a point then make that point, don't make a different point and get surprised that none of us are psychic.
And no, it wouldn't. People have this weird thing with MCU characters like "oh, they've BEEN supporting, therefore they couldn't possibly lead their own movie" and it's a false narrative. Just because it hasn't been done before doesn't mean it wouldn't work - people really like her character. A movie could be a prequel or a modern-set spy movie with MCU tie-ins. Dwayne Johnson's been supporting in three Fast movies, he's getting his own spinoff.
Not only that, people don't take into account that it's about profit margin, not the total box office gross. A movie like Black Panther might clear a billion at a cost of $250 million or so - Black Widow could cost $100 million or less (think about the CG compared to Doctor Strange or Guardians) and if it makes 600 or 700 million it's still a big success. Doctor Strange didn't have that much higher of a box office than Justice League, but it cost half as much.
Let me guess - you were one of the people screaming over and over how Guardians was gonna bomb because it was an unknown group with no A-list actors in the main ensemble. Then you switched to screaming about how Ant-Man was gonna fail because it's a "D-list character that's considered a joke" and because Edgar Wright left. Then you moved on to Doctor Strange.
Woah! Pump the brakes haha. Was the essay necessary? Rationalization seems bit reactionary, nothing I said was intended to offend you. So many incorrect judgements here. Explaining my logic so I am understood is not a defense, just an attempt to literally avoid this kind of reaction.
But just so we are clear,
Screaming over and over..no, I don't have that kind of personal investment in these movies, but since you asked
1. Guardians of the Galaxy - was my most anticipated phase 2 movie mainly because "Annihilation" was my favorite Marvel crossover ever, which featured both the Guardians, and Ronan. Infact, Ronan's arc made me a huge fan of the character. Knowing Thanos had a role just made me more excited. So, no, I wasn't screaming about how it will bomb, I was happy to.righteously defend it at the time.
2. Ant-Man - I was excited to see the special effects, and the in universe scientific explanations for the suit. I was also curious to how Hank Pym would be incooperated into the MCU, not being Ultron's creator, and the modern day Ant-man. I remember being stoked to see the subatomic stuff as well.
3. Doctor Strange - I simply was beyond excited to see this movie and was my most anticipated movie since Avengers 1, for me personally and it met all my expectations.
Widow has been a supporting character for quite a few movies, and that's why I felt the movie would be less successful than other MCU films. Was "bombing" the wrong word to describe this? Yes, clearly. That's on me. I've said this already; my stance as a fan is not what you are seemingly try to mold me into here.
However, if you want to continue to incorrectly take guesses towards my logic and rationale and overreact about my fandom, despite me (again) explaining in better detail my reasoning for my take, that's on you. You're entitled to that, and I'm not going to tell you, you can't. But I won't continue discussing this because it isn't necessary. Have a nice afternoon.