I think this is true in the already-ad-saturated environment. But if we imagine a world without ads, it's hard to think there wouldn't be other ways of getting a product out there.
One obvious way is through buyers. A lot of clothing and housewares brands, for example, don't advertise significantly. Instead, they shop their wares to buyers for retailers. Another is through reviewers. Electronics companies, for example, have a long tradition of sending out gear to magazines and other sources of reviews. Car magazines are another good example. In the modern age, that also can mean lending or giving gear to people influential in an area.
If ads didn't exist, I think we'd see more of that. And we'd certainly see more of other approaches. Look at ProductHunt, for example, where startups can put things in front of a crowd of early adopters for nothing. It would be pretty easy to imagine specialist versions of that for particular interests. And look at Tesla, which famously didn't run ads; plenty of people have heard of them.
So I agree you're right that some new companies today could be at a disadvantage if they don't buy ads (although definitely not all of them). But I'm not convinced that's a necessary case if we end the ad arms race.