I've been maintaining my personal website as plain HTML for five years now. I must say, I quite like this method. There's no substitute for practice when it comes to maintaining your skills at editing HTML and CSS.
Yes, you must copy and paste content and not having layout page is annoying at times. But the overhead of just doing it yourself is surprisingly small in terms of the time commitment.
Typically, I'll draft a post in MS Word then open the git repo for my site, hosted on github pages, duplicate and rename the template.html page that includes the CSS, footer, and header for my site and then copy my content into it. When I'm happy with everything, I'll make my commit and then a minute later it's live at my custom domain. Seeing that it takes only 11KBs and 26ms to load my landing page strangely delightful.
Impressed that this runs on my RX 6900XT (an RDNA2 GPU) in Chrome without any trouble. Very cool demo, excited to see how people leverage this capability.
I used this stack to replace a Django/Python app that was built over 2 years by another dev in 2 weeks. We regularly have 1 hour turn arounds between when an issue/feature is filed on Github and when a new build is live with that code. The self-contained deployments have made it simple to deploy this app, and now its supporting apps, to our linux-based cloud instances.
I've built on many stacks and although I agree that iteration speed is important; It has more to do with how you organize your project and the quality of your tooling than with the specific language/framework.
If you don't like the OOPy style, don't write in it. Pattern matching in C# is quite nice, and you can always mark you functions as static. As a bonus, simple functions are easier to test to.
My favorite part is the tooling. For example when you hover over a method name in VS 2019 it will show you its signature and what parameters it takes. If you right click on it and select "Go to definition" it will show you the code for the method. Just above the method name you'll a little chunk of text that says "2 References" which you can click on to see all of the places in your project where the method is invoked and links to review them. What makes ASP.NET fun is the quality and completeness of the tooling.
Make sure you have a plan to upgrade all your projects to .NET 5.[1]
ASP.NET is quite fun, if you can keep your work up to date. Opening up a project that needs bug fixes, but doesn't have access to the latest tooling in VS2019 or language syntax because it still on the old .NET Framework is a bummer.
Any company that was willing to update their .NET apps regularly, and treat development of the app as a service rather than a one time project would make me jump ship.