if you have large number of pages i.e. 1000+(its not that far fetched with documents) most of react/vue based solutions struggle in generating them in the sense that it takes long time to see output for any change you make.

Its question o familiarity if you are not aware of react than it would take even more time for you to learn it and use it than ssg frameworks.

you can still use your familiar html/css/js if you want to without learning whole ssg almost all ssg frameworks provide a way to code html/css if required.

ssg's are battle tested when it comes to myriad seo features like twitter cards/og/json-ld/schema etc. which are proven to be working in the field. When you go for rolling out on your own you will end up in solving lot of edge cases that different platforms(twitter/fb/google) have that would result in cover image not being displayed properly to site not appearing in google etc.