Can I be completely honest? After all these years of watching the Twilight movies, I never really minded Kristen Stewart's portrayal of Bella. I've always liked her mannerisms in the role. She captures the little tics and awkwardness of someone who's socially insecure, spends a lot of time alone, and genuinely sees herself as uninteresting. It always felt more authentic to me than a lot of modern teen performances that are supposed to be "awkward." Just look at a lot of Netflix teen shows lately as so many "awkward" characters come across as quirky, witty, and effortlessly charming that it ends up feeling a little too manufactured. There aren't many performances that actually commit to the discomfort and social awkwardness the way Kristen did.
Was it the best performance she's ever given, or even the best in the genre? Maybe not. The corny dialogue and often stiff direction definitely held her back at times. But was it the best portrayal of who Bella was supposed to be? In my opinion, absolutely.
So yeah, in retrospect, I think Kristen Stewart was perfectly cast as Bella.