[0] https://pytorch.org/tutorials/beginner/deeplabv3_on_ios.html
How much did this change after the big Meta layoffs? I think I know people who are no longer there, but I haven't talked to them about it yet.
But whatever their code quality may be, luring in devs to their API has seen hits and misses.
The stereotype of Google back then was very different. People would quote things like "don't be evil".
That doesn't automatically have to mean better DX. For example the API can be clean, but too low level to conveniently accomplish typical cases (I'm not familiar with this example).
While I'm not going to disagree that it matters, to my mind the main thing about early (0.x, 1.x) PyTorch's success was a clear vision (most visible to me from Soumith and Adam) that put the targeted users first (as in your productivity comment), awesome execution on it, and a creating a community where I, as an outside contributor with modes skill and no AI track record, and likely many others, felt welcome.
Now, the many great people employed by Meta, but also other players like MS, NVidia, AMD, Intel, ... to work on PyTorch enabled all the things that make PyTorch 2.0 nicer and more broadly applicable than 1.0. (And to my mind it's quite a non-trivial accomplishment to enable other corporate players to join the party.)
Another lesson is probably old but worth repeating: investment and professional polishing matters to open source projects. Meta reportedly had more than 300 (?) people working on PyTorch, helping the community resolve issues, producing tons of high-quality documentation and libraries, and marketing themselves nicely in all kinds of conferences and media.