We do exactly this within SharePoint. We have various react parts that look things up in the database - sometimes quite heavy queries for reporting.
We have put together a small collection of fairly generic react apps that mean we can put one on a page, put in some config and have it displaying a report generated in SQL in about as long as it takes to write the SQL for the report. We have used this approach for generic SQL reports, SharePoint lists, imgage retrival and entry forms. Having the library of options to hand has meant we can confidently assemble a new (fairly complex) page much quicker than previously - and be confident that it will work as it is reusing known good components.
We have put together a small collection of fairly generic react apps that mean we can put one on a page, put in some config and have it displaying a report generated in SQL in about as long as it takes to write the SQL for the report. We have used this approach for generic SQL reports, SharePoint lists, imgage retrival and entry forms. Having the library of options to hand has meant we can confidently assemble a new (fairly complex) page much quicker than previously - and be confident that it will work as it is reusing known good components.