R Markdown is one of the more compelling aspects of the R ecosystem, making it easy to incorporate results of R code into a text. Plus, R Markdown files can be exported to a variety of formats—Word, HTML, PDF, PowerPoint, and more. You can even export complete books and websites.
But R Markdown has been around for 10 years. And as more capabilities were added via external R packages, syntax for basic tasks became inconsistent. For example, code to add a document theme depends on whether the output is a stand-alone HTML document, HTML slide presentation, or something else. Plus, while you could run additional languages besides R within an R Markdown code chunk, it still was fundamentally built for R.