1. Advertising ideally works as match making by connecting buyers to sellers where the seller is unaware of the buyer. (i.e. the unknown unknown problem). Companies usually collect advertisements and place them on limited ad slots.
2. In earlier, physical, forms of advertising such as newspapers, TV, Retail Stores etc, the same ad used to be shown to everyone so ad slots were fewer, much more expensive, and typically only big businesses could afford them.
3. In Digital ads where ads can be personalised to users, there are now a lot more ad slots and small businesses could effectively reach out to niche buyers who otherwise wouldn't be aware of them. The ads are thus cheaper as their budget is better focused on the right users.
4. Digital ads are broadly of 2 types: Intent ads, where the user submits their intent (Eg: Google search, Amazon, Maps etc) or Discovery ads, where the user is typically not present for any single intent (Eg: Facebook, Twitter, Instagram, YouTube etc)
5. Discovery based ads in particular can help open up completely new behaviours (in an ideal world) where the seller wasn't aware of the buyer's product but found it very useful (i.e. The unknown unknown problem)
6. Both Intent and discovery ads can be harmful to the user. Intent ads basically charge a tax to prioritise their results (i.e. rent seeking: pay more to jump the queue). Discover ads degrade the user experience (i.e They could've shown you something more interesting but decided to show you something less interesting to you and received money for it from a 3rd party).
Some opinions below:
1. Making digital ads more like physical ads (Eg: By removing personalisation) will probably benefit big businesses by increasing ad prices and making it harder to match sellers to buyers. It's often small businesses who have a niche which increase competition in a market (The Innovators Dilemma)
2. In the EU's case, the ads can be personalised, just not based on behaviour but on context. So this will probably still increases prices but still not change digital ads fundamentally (i.e. they can still be personalised somewhat to the user) at least for now.