Yes and no. Our behaviors are a result of habit. Our reactions are a result of habit. We can form habits that help us or harm us. I do think there is a lot of stuff that is innate - like I'm going to always think about how to do things better and improve stuff. I'm not going to change that. Negative things though, I would endeavor to change.
Even if the majority of character is determined and not ontologically a priori there still remains some behaviour that is, attachment behaviour, for instance, is just one example, its come a long way from the first observations of ethologists, or Darwin's observations of emotion in man and animal, and evolutionary psychologists.
The thing about that "some behaviour" though is that I suspect its consequences are massive, even if the development of habitual behaviours as a consequence of attachment styles and internal scripts stemming, attributional or explanatory styles as compensations for attachment deficits or disordered traits is hugely exaggerated its pretty significant.
No one interrogates the whole Skinner Box mentality of "its all nurture" the way they are willing to dismiss "its all nature", which I think it telling.
Personally, I think its because a lot of natural law or naturalistic theorising just does not sit well with a lot of modern manners or fashionable opinions, now, there's a lot of different reasons for that. I think most of it is reflects hopeful, best/good intentions, I wouldnt fault it but its a little like honestly and seriously expecting a wonder drug which will guarantee longevity akin to immortality and eternal youth with it, its a really nice idea, I just dont think its anything other than imaginary. Also some it is an addiction to novelty, perpetual change, the shock of the new, leaving no avenue unexplored or unexperienced, directly, which I think in turn is a result of consumerism and its unconscious engineering.
I'm not saying you're doing it but I encounter the "its all beliefs anyway, none of it is fact" all the time, its short hand for not wanting to think too hard or too long or too deeply about any of it. Its one of my triggers because while skepticism and doubts and falsifiability are all great things up to a point, after that point the denaturing of mankind is nothing short of flat earth thinking. Often by people who'd pride themselves on being anything at all but capable of that sort of thing.