How hard is it to create a basic website builder?

I built https://versoly.com/ a website builder.

It is pretty easy.

Use any backend language.

Grapejs.

And you're good to go.

Issue is adding new features, reliability etc

Never built a website builder, so I cannot know for sure. If I took this question like any other idea I would like to validate or product to build, I would break it down:

• Are there any services/APIs that would allow me to deploy a website using code? Maybe I can do this manually instead?
• What is the easiest/cheapest way to give my users the ability to create a site without code? Do I need code for that? I remember seeing a project building websites by taking a photo of a piece of paper, so anything can work.

You mentioned 'faster' but that's subjective. Is this for an MVP? Validating ideas? Full blown product? etc

Seems like a crowded market.. are you targeting a niche?

I haven't created a website builder yet but i did with html email builder. At first I started with grapesjs, but I found it quite difficult to customize and had some issues. So I decided to make one for myself. I defined the possible components for an email, each component will include its own configuration, and I get a json structure of an email, then I use react-beautiful-dnd, custom it, to create a drag and drop that can generate json configurations.
After getting the configuration of an email in json format, I generate html from it (actually I use an engine to generate html, you can make your own).
It took me about 2 months to create a complete tool. However, to create a website builder I think it will take longer because it has more components.