I think the implication here is "that honestly doesn't seem that important" because the expectation is that the number of people who would find you anyway would be a small number compared to a well-run ad campaign, at least over timeframes startups care about.

Having worked with a decent number of small teams without a lot of brand recognition, ads bring in a lot of customers: it was pretty obvious in our metrics when we ran ad campaigns vs when we didn't. Sure, eventually a few of those people may have found their way to us somehow anyway, but there was a step change in volume from ads. At least in my experience, the idea that ads have no significant impact is not really supported by the evidence. I assume that's what the OP meant by it not seeming important: they're working under the assumption that "do any ads do anything" is clear and you don't need to prove the worth there — instead you need to prove which ads work better than others, and cull the ones that don't perform well (which will also help save you from scammers).

One could argue that advertising for large brands with name recognition could be less valuable. I don't really have data or experience to know that one way or another, but in a competitive market that seems a little hard to believe. Tesla is an interesting counterexample, but I think it may be in part due to the EV market in the US not being particularly competitive; no one makes attractive, mid-priced cars with long range other than Tesla, let alone having an established charging network for road trips. And Elon's antics are, tbh, a form of marketing in and of themselves; "all press is good press."

Edit: I wrote the above paragraph badly. I can definitely believe ads are less valuable if you're a big brand vs a small one. But I'd be surprised if they're useless, at least in a competitive market. People don't have infinite money, so if they're looking to buy X and an ad for X from your competitor pops up, it seems reasonable to me that some percentage of the time your competitor would make the sale and thus you wouldn't, even if organically that sale might've gone to your company instead.

Also, I wouldn't argue that even small companies need ads — just that they do seem to be effective at increasing the volume of people interested in using your product at a given time. That may or may not be necessary/useful depending on your situation. I have been on teams where we intentionally turned off ad campaigns because we learned what we needed to learn from the cohort of new users, and now wanted to improve the product based on their feedback before spending money on more ads.