I’ve been in that situation before, and most of the time it’s not one big issue, it’s a mix of small basics not being fully optimized. Things like page titles, clear structure, internal linking, and content that actually answers user questions usually make the biggest difference.
When I was working on a project and trying to understand what is automotive seo, I realized results didn’t come from tricks but from getting those fundamentals right and staying consistent.
Start simple, fix the basics first, and build from there.