I don't read this as "it was a mistake to use Pony." They state that:
> in the meantime data science and machine learning continued to explode ... With the increasing focus on MLOps, Rust became a better fit
This sounds like, "Our business goals shifted, as did the industry around data science, and Rust's maturity improved such that it made sense for us to migrate our stack."
Mistake or not is hard to quantify without presenting what qualifies as success first. Is "it was able to achieve our initial goals" success or is "it was able to grow with our business" success? For each of those how much ability is enough to call it "not a mistake"?
I think it's fair to say looking back it was a mistake to pick Pony on the assumptions it provided marginal benefit for the exact needs of the business day 1 but at the same time I think it's fair to say that picking Pony was not a mistake as it allowed them to get where they are today.
> in the meantime data science and machine learning continued to explode ... With the increasing focus on MLOps, Rust became a better fit
This sounds like, "Our business goals shifted, as did the industry around data science, and Rust's maturity improved such that it made sense for us to migrate our stack."