Doesn't need to be a single person, but yes, all good products come from someone or a (generally) small team, spotting something, and fixing it.

As for the marketing department - depends on definition, but assuming you mean (as it mostly is nowdays) comms, it's two things:

1. Making sure that potential future customers know you exist, so when they enter the market to buy, they know you're relevant and can purchase from you.

2. Making sure that when someone is in the market to buy now, that they're more likely to buy from you, because you have a compelling reason for people to pick you, and not the other brands in the space that they can think of.

Mostly 1, some of 2, if the marketing team is good. Ratios vary as to how much though by more than you'd think, depending on industry, customer lifecycle, brand maturity and so on.

Good segmentation is mostly not by demography nowadays. At best, demographics are a correlative element to something more fundamental, usually economic, behavioural or psychographic.

"how come no one, in the past 25 years of my life as a consumer, has ever had any time to ask me a single real question"

There's a lot of shit marketers, is my short answer.

Like, a lot.

The problem I tend to see is that companies say they're doing JTBD research, but they're actually just running attribute preference surveys (asking customers to rank features, from a list of things the company would like to build, rather than starting off by assuming you don't know what customers require).

Listening to what people say they want (feature preferences) almost always diverges from what they actually want the product to do (a functional, emotional, or social outcome). That gets more complex when we think about that there's different levels by which you can evaluate what someone wants, which in the JTBD word are thought of as jobs as progress (why they're doing the thing), and jobs as outcomes (how they're doing the thing). There's another famous example, which is from Bosch's circular saw evolution. Professionals said they wanted lighter tools (and that's true), but the constraint they experienced as a result of weight was the impacts that had. So you can solve for weight, or you can solve for improved usability. Symptoms vs causes sort of thing.

This is also why product teams should involve marketers, and why marketers should understand research design. The teams who I've seen do this well at this aren't running quick preference tests and A/B tests on features most of the time. They're generally more focused on running continuous feedback loops, where they conduct broader research, then engage in grounded theory style interpretation to understand what they can do, look at field validation to figure out what they should do, and then iterate.

For B2B especially as a side note, if your value proposition is something like accountability or proof of value, but your product's workflows don't make accountability or proving value effortless, fixing that workflow will do more for brand perception than any campaign, because nothing nukes good comms like a poor experience.

It's what always happens when there's a disconnect between the product built and the actual thing people want to do. In marketing, we differentiate between Jobs-As-Activities (the task of "changing a background") and Jobs-As-Progress (the user trying to go from something being unsatisfactory to something better).

When UI feels dumbed down to that level, or hidden behind advanced settings, it’s often because the product team ends up treating users as a gestalt persona, rather than thinking about their constraints around time and attention. The most meaningful innovations occur when customer insights influence development before launch; sadly, that frequently doesn't happen. People launch the thing, come up with features they could add, ask what people want from that list (and potentially don't even do that) and then add stuff like barnacles accumulating on a ship.