In fact, many marketplaces find that basic things like photos, prices and descriptions are already worked out, but this doesn't always guarantee an increase in sales. In such a case, it makes sense to focus on conversion rate optimization (CRO). This is not just about improving the appearance of pages, but a whole process of testing and implementing solutions that work. There is a cool service that just specializes in such tasks
https://conversionrate.store/marketplace-conversion-rate-optimization-services/. Their trick is that they work on a pay-for-results model: if they don't achieve the stated increase in conversion, they continue to work for free until they achieve the desired effect.