For one, while certain websites or apps show a clear signal that can be used (e.g. coding, hence the user can be shown ads on coding tools), many other websites or apps are not giving a signal on preferences or intent, this besides the ads inventory being an issue.
For example when you're reading political news, or when you're playing chess, what ad could you be shown that could be related to politics or chess? I can answer this - without a user profile, best case scenario is that you're shown something at random, with a disastrous conversion rate. And worst case scenario is ads being used for spreading pieces of propaganda on controversial issues and I remember for example how a certain gold mining company was attempting to manipulate with downright lies the viewers of certain YouTube videos that were criticizing their open-pit project. And because such ad spots are basically worthless, they can be bought for cheap.
I'm personally all about privacy and the security of my data, being downright paranoid. But privacy is one thing, blocking ads is another. If you don't like ads, then don't use those services or websites. That's how you end up rewarding alternatives and personally I rewarded many alternatives that way. Even if you want to punish bad actors, you still give them the eyeballs, you still distribute those links to your friends, etc. The concept of voting with your wallet is basically broken.
And contrary to the music and film industry that has pushed for DRM, this time people that block ads don't have the proper moral ground to stand on and also the industry is not going to go down without a fight. Consider that you can't block ads in mobile apps without having root privileges. This will turn out to be a whack-a-mole game and it won't last for long. Just wait until these websites will start to serve ads from their own domain, with ads being indistinguishable from the surrounding content ... oh wait, this is already happening ;-)
Worst of all is that you end up hurting other people - from publishers, many of whom are already on the verge of bankruptcy, to people that will suffer the consequences even if they don't use ad-blockers, as the history of video gaming can teach us. Do you enjoy the DRM laden pay-to-win gaming industry that others have created for you? As personally I'm thankful that I've outgrown video games.