Originally published on Medium — celestia-studio.fr
I've rebuilt 4 AI-generated websites from scratch. Here's exactly what broke.
In February 2025, Andrej Karpathy, OpenAI co-founder, posted on X: "There's no coding, only vibes."
Vibe coding was born. Since then, thousands of entrepreneurs have tested tools like Bolt.new, Framer AI, or Durable to build their website in under 30 minutes, no developer needed.
The visual results? Often impressive. The business results? Usually terrible.
I run Celestia Studio, a Webflow agency based in the south of France. In the last 6 months, 4 clients came to us after trying AI website builders. Every single one had the same problems. Here's what I found.
Let's be honest. These tools are genuinely useful in specific situations.
Validating an idea fast is the obvious one. Durable.co generated over 1 million websites since its 2023 launch. That's real demand for speed. Temporary landing pages work too: product launches, webinar sign-ups, event pages where SEO doesn't matter and the page disappears in two weeks. Same for personal portfolios with no conversion goals, or internal prototypes you're showing to investors before committing to a full build.
For these use cases, vibe coding is a legitimate tool and a real time-saver. Here's where every AI-built site I've reviewed breaks down.
SEO structure. AI builders generate pages that look professional but are structurally broken for search engines. On 10 AI-built sites reviewed by SEO experts in 2025, 9 had critical structural errors preventing proper indexing. The pattern is always the same: multiple H1 tags on a single page, generic or duplicated meta descriptions, no alt text on images, zero internal linking, non-optimised URLs. Google sees none of what actually matters.
Core Web Vitals. Google has included performance in its ranking algorithm since 2021. AI-built sites consistently score 45 to 65 out of 100 on Lighthouse. A properly optimised Webflow site scores 85 to 95. A site that loads in more than 3 seconds loses 32% of visitors before they read a single line of content (Google, 2024).
Conversion. The average conversion rate of a professionally optimised website sits between 2 and 5%. The average for an unoptimised AI site is under 1%. On 1,000 monthly visitors, that's the difference between 10 and 50 leads. Forty potential clients lost every month. AI tools place buttons. A conversion expert places arguments.
GEO, the layer nobody talks about. This is the one costing businesses the most in 2026. GEO (Generative Engine Optimization) is the practice of structuring your content so AI systems like ChatGPT, Perplexity, and Google AI Overviews can extract and cite your business in their answers. It requires Schema.org markup, structured data, and content formatted for extraction. AI website builders don't implement any of this. Sites without proper Schema.org have 40% less chance of appearing in generative AI answers (Princeton / Georgia Tech, 2023). For any local business trying to get recommended by AI in 2026, that's a structural disadvantage baked in from day one.
Each one came to us after 3 to 6 months online with an AI-built site. Zero Google indexation. No Schema.org. Lighthouse under 60. No leads.
We rebuilt each site on Webflow, kept the visual direction they liked, and added the strategic layer that was missing: SEO architecture, Schema.org, GEO optimisation, conversion structure.
One of them went from 0 to 3 Google Featured Snippets in 2 weeks on a 3-month-old domain, with zero backlinks. The content was just structured correctly from the start
Ask yourself one question: does my website need to generate revenue?
If yes, you need a strategy, not just a visual. An AI tool builds the shape. An agency builds the engine.
If your site is a test, a placeholder, or a personal portfolio with no commercial stakes, vibe coding is fine. Genuinely.
But if 40 lost leads per month is a number that matters to your business, the maths on a professionally built site are straightforward.
Enzo Marcelle is the founder of Celestia Studio, a Webflow agency specialising in SEO and GEO optimisation. Based in Agde, France