First of all, if you don't practice any tracking limitation, you're almost certainly giving additional parties (directly or otherwise) access to your personal information. This is marketing data brokerage, this is the whole ballgame.
To your point about the actual harm, I've come to see it as a kind of ecological problem. Wasting energy and sending more trash to a landfill doesn't harm me individually, at least not immediately. But it does harm in aggregate, and it is probably directly related to other general harms, like overall health outcomes, efficiency, energy costs, etc.
No, accepting cookies by itself may not do much to me, but the broader surveillance and attention economy that relies on such apathy certainly has.
I hear what you're saying, and instinctually I feel gross about it. But, if enabling advertising allows the website I'm visiting to stay in business, I think that might be a trade-off worth making.
Do you have any napkin math on the ecological impact in quantifiable terms? I'm just super curious what the scope of the problem is.
I turn off 3rd party cookies in the browser but I don't see first party cookies as big of a threat and I click accept just in case it breaks the website somehow.
The effect of that data is serving you better ads. Its not a big deal. Dystopian governments have way better sources of citizen data than anonymized ad exchanges. It basically just powers product discovery in a giant global marketplace.
Sadly, this still doesn't do anything to show me that I should opt out.
I, as an individual, am not going to have any effect on a business if I opt out or not. No business decision is going to be made because I opt out.
You might argue that it will matter if enough of us do it. Sure, that is true... but again, it won't matter if I do it or not. If N number of people opting out is enough to ruin the business model, then N-1 is surely enough as well. There is a 0% chance that I am the one who finally causes the system to collapse.
I do use an ad blocker, and never click on ads. I feel like that action has a bigger return on investment than no clicking the cookie banner.
If having more information about me allows the website to charge more to show me an ad, and I never click any ads, then I am hopefully helping decrease the return advertisers get by using personal information.