Earlier quoted context omitted.
> At first glance, this appears to be much more complex. React is a relatively simple DOM diffing library. Their implementation is 2k lines of code. The React repo has 350k lines of code. The Rails repo has 336k lines of code (both of those according to tokei). Of course this includes tests, lots of other stuff, etc. But still, that's two orders of magnitude.
Note that react has a monorepo with a lot of tangentially related packages, such as devtools and alternative renders.
That's true, it's hard to make a fair comparaison between the two.