[1]: https://github.com/boringdesigners/boring-avatars/blob/maste...
It's all open source. If you want a vanilla js implementation go ahead.
https://w3techs.com/technologies/overview/javascript_library
React is a small part of the web(in terms of the number of people using it commercially) and thus a library written in React isn't terribly useful for most of the market.
And why does that matter? The OP is someone's toy project, not an attempt at starting a SaaS company.
In this case, I guess the developer wanted to use JSX to create it. And you could ofc use JSX without React. But most people are used to using it in react-context, and plan to use it in an react-app anyway.
So to answer your question, in my eyes it would be. Why not? If the devs plan on using it in react-app anyway, it's not their job to make sure it supports everyone elses usecase.
I have no problem with people writing code for themselves. But if that is what you do, please don't post on Hacker News about it.