The best competitive research I've seen goes beyond the competitor's website, press releases and YouTube videos. They might include competitor customer interviews and tailored sales demos. I've personally worked with great small businesses and consultants who are experts in doing this analysis and research. If you have a little budget, I'd recommend that path.
Not sure what mark you're missing. But your CEO and product/eng team are probably looking for (1) an overview of the space, where everyone is going (2) highlighting a few players and going deep dive into why they're building it and who they are building for. [I would hire a secret shopper for the second part]
To establish credibility with a new team, the first step is understanding the team's need, laying out a vision for how you can best add value, and aligning around expectations. It is important to know the user, the market, and the product so that you can engage with the cross-functional team in a meaningful way from day one. With a clear set of objectives and foundational understanding of the space, you can quickly begin to make an impact on the team.
The definition of "Extensive competitive product research" may be different for different people. I suggest asking the CEO and Product / Engineering teams the kind of questions they are looking to answer. Sometimes the high level market research you can get from a 3rd party will not be enough, and you will need to get creative to get the information needed via surveys, primary research or other methods. My best advise here is to define the task in more detail to undertand what people are expecting.
Sales and customers will be your most vital partners for this task. They will have likely have had multiple run-ins with your competitors. As a result, they will give you an excellent high-level understanding of competitive pitches, pricing, what attracted customers to them, and how the market, in general, perceives them. When you want to go deeper on a technical level, SEs, TMEs, and other PMs will be able to assist you with a feature-to-feature comparison, but keep in mind to approach the problem from multiple angles to get a better picture.