If little can do a lot just imagine what I can do with few megabytes: Google Gmail/Youtube engineers
Or rewrite react yourself as another commenter already did.
Depending on the scope of the work, this is not allways a bad thing. I like my own framework. It does exactly what I want and I can tweak it to my needs anytime.
But I work alone and don't have to share my code with different developers, otherwise there would be problems ...