I think my father got scammed by an SEO agency - what can I do to do help?

Hi /SEO community. My father who currently runs a e-commerce store specializing in golf gloves had told me that worked with a local SEO agency for the past 2 years or so providing him SEO services. He told me he paid close to $3,000 a month. I work in the SEO industry myself and after doing some digging into his site, I felt a bit skeptical with how things were considering that URL slugs were not even optimized, there was no content to be seen at all on any of its category pages, bunch of typos across the website, etc. In addition, a very basic 'About Us' page is nowhere to be seen and it looks like they hardly put in any work into providing honest SEO services. According to my father, there wasn't a single time where they had reported anything (whether it be weekly or monthly) which raised an immediate red flag. I wonder if a clear scope of work was even provided from the beginning. Looks like they were also running Google ads but the ROI just wasn't there and his marketing budget pretty much just all went to waste. I'm busy with work and life myself but I want to help my dad reach his goal of growing his brand and eventually racking in the sales that he wants although that's clearly going to take time and hard work. I don't even think the site was built from an actual CMS from the looks of it and I just think the overall user experience is not the best either so I was thinking if it'd be feasible to just start the site from scratch all over again on a SEO-friendly CMS like Wordpress, I honestly am not too sure. If anyone could lend a hand to see what would be the best course of action from this point, I would very much appreciate it. Thank you.