My very loose understanding is that the effectiveness of the "Not interested" button is somehow inversely proportional to the strength of the correlation that TikTok uses for that particular suggestion.
As the obvious example, if you are a male, you might only need to click "not interested" once or twice to stop seeing e.g. skateboarding or woodworking content, but many, many times to stop seeing content from attractive females.
I suspect it 'knows better than you'. Self-curation leads to a boring niche whereas ignoring what you want in favour of what you linger on - even if you're lingering out of rage - leads to more engagement.
As the obvious example, if you are a male, you might only need to click "not interested" once or twice to stop seeing e.g. skateboarding or woodworking content, but many, many times to stop seeing content from attractive females.