Thought-provoking questions! For me, ad-tech creates a few interrelated concerns:

1. Pervasive, asymmetric surveillance increases the power differential between individuals and big corps/governments. The latter groups can use that power to preempt healthy competition, causing individual quality of life to stagnate in a local maximum.

2. Ads themselves are attention hijacking, thought injection, and manipulation/coercion—all forms of mind control. Most people consider their mind central to who they are (often along with body, memories, and personality), it's wrong to mess with that non-consensually. (No, clicking "accept ToS" isn't consent.)

3. Centralizing surveillance data (as by companies and governments) prevents the surveilled from protecting their own vulnerabilities from bad actors. It's like passwords: you can invest in memorizing many strong ones, or re-use one that's written on a post-it on your desk, but since in this metaphor the surveillants are also storing your password in plaintext in paper filing cabinets, so it doesn't matter how much effort you put into protecting your passwords. Put another way, if the Coke recipe or a Boeing blueprint were leaked, it's the company's loss, so they work hard to protect their secrets. But if someone hacks a consumer company's user data, it's the users who are affected; if it weren't for regulatory fines and news exposés, companies wouldn't even be hurt by such breaches.

As for the end-game goals: Companies surveil and advertise because they're allowed to and it works.

We see futuristic attention hijacking tech in sci-fi films and TV, like giant holograms [Blade Runner], ads that address each individual [Minority Report], or ads that stop until you're paying attention again [Black Mirror]. But it's less common to see futuristic attention protection tech. (That makes sense if you consider the funding source of these sci-fi productions.) Black Mirror did have one episode where a person was exiled from everyone else's senses, but I can't think of others.

[It works] The individual's goal could be total control over perception of the world. As a natural-born human, you can easily close your eyes, but your other senses are harder to dampen, and so provide vectors for involuntary thought injection (ads). Now with widespread earbud use, you can sort of close your ears too. But imagine installing an ad-blocker so your senses just didn't report ads, or your brain didn't perceive them? As with many technologies, it'd be quite dystopian if centrally controlled, quite freeing if under individual control. Even more fantastical would be the ability to experience but be unaffected by stimuli (including ads), which might not even be a technology exactly.

[They're allowed] The other goal could be simply to use our collective power (i.e. government) to more strictly regulate—or even ban—surveillance and advertising (and enforce it!). While this always possible, I'm afraid it's no longer realistic in U.S., though other countries could still pull it off, as could whatever government eventually replaces the American one.

Lastly, what if nothing were free? Part of the problem is that the difference between $0 and $1 is much, much larger than from $1 to $2, i.e. free is a way better price than even dirt cheap (or sometimes even being paid). Tech start-ups are especially guilty abusing the marketing power of "free" in combination with unsustainable infusions of venture capital, which is dishonest if not somewhat fraudulent. Business would survive the removal of tactics like "free + ads" and "loss leaders".