For a good overview of what power and speed you can have by "putting a web development platform entirely inside an RDBMS", check out this video called "Twitter-like App in 20 minutes with Oracle APEX"
My answer is probably seen as unconventional on Hacker News, but keep an open mind and you'll be pleasantly surprised.
I suggest you sign up for a free account at https://apex.oracle.com/ to try out Application Express (APEX). It's a free, web-based development tool for building modern, responsive and secure web applications.
Since all these features are built in, you don't need to go shopping for the usual mix of libraries, build tools, external services, etc. For 95% of what you want to build, it's all there already as part of the framework.
The best thing is that you can get started and be developing web applications within minutes on this platform, without writing a single line of code. Even though you start out with no code/low code, you can add as much code as you want and go to any complexity later. The framework doesn't stop you from going "full code".
Also, if you are worried about vendor lockin (any more than AWS or Azure or Google or whatever "framework du jour" locks you in), it should be noted that you can download and use APEX for free on your own infrastructure (or a DigitalOcean droplet or whatever). Also, APEX can run on the Express Edition (XE) of Oracle, so you can build and deploy web apps without ever having to pay Oracle a single dollar.
https://www.youtube.com/watch?v=bosMSghczUo