- accessibility
- amount of libraries with plug-and-play solutions to common problems
- security
- scalability
- rendering performance
- maintainability
- browser support
- browser extension interference
- hundreds of other niche edge-cases that someone will eventually run into but are non-obvious until it's widely used
React is really well-thought out and well made by hundreds of professional contributors that have worked on it for years. The premise that hobbyists can make a better overall solution in less than 8 months is strange. At best they can make a smaller solution, but it will have to sacrifice in other areas.