It’s not a matter of ambition or lack-of. Nobody is going into a 100k+ company and just changing the entire corporate culture around something as broad as bug fixing. These companies have hundreds of teams, and decades of entrenched culture. Sure, go in and improve what you can in your own lane, but be realistic about your scope and reach.
Nobody ever changes anything and new hires should have no aspirations or goals but to be code monkeys.
Your outlook on career growth is nihilistic, not realistic.
Your outlook is not realistic.
My outlook is "Sometimes if you have ambition and opportunity, you may be the person that can make things better."
I have made no claim or assertion other than that. If that's not realistic to you, then I sincerely and genuinely would advise you to seek therapy, because that sounds like depression.