SSI.
1. dependency on your host/server for support- ie can you do this on s3? Netlify? Gh pages?
2. No way to embed content inside an Include
3. No easy way to apply additional transformations, eg html post processing
This method only gives html pages as output, with no runtime deps
It is pretty basic, however. Just templating and kicking off scripts. Still helpful as a lowest-common-denominator tech.