If anything, these companies probably welcomed these regulations and now have more power over politicians who have used up much political capital in getting this done. It's unlikely that any corrective actions will be taken anytime soon.
Oh, they'll find things. There are already active formal investigations by GDPR authorities in various countries against Twitter, Facebook, and Google. The companies do like GDPR, as the fines will be nothing more than a small tax on their massive revenue. It's a win for both the companies and the politicians: the companies get a monopoly in exchange for a small tax in the form of fines, revenue hungry EU nations get multi-billion dollar windfalls, and EU politicians get to look like defenders of the people who will be tough on US companies. Everybody wins, except for would-be competitors and the consumers that don't get any choices about the services they use.
Meanwhile, all other marketing companies are further blocked from interacting with users because of the lack of consent and direct relationships. This makes the existing monopolies even stronger, and makes it much harder for newer companies to even attempt to compete.
But of course, most adtech services do make use of a multitude of private data for profit, and that's why they are having a hard time.
The company I work for (Teachable) is a specialized site builder for course content. We make all of our revenue from people either paying us directly for a plan, or transaction fees on people buying from our customers, no ads or data selling. Nevertheless, complying with GDPR still took well over a month of some of our best engineers time. Even if you don't sell data, the odds you had a plan prior to GPDR for how to handle right to be forgotten - how do you delete PII (which is defined broadly, including ip addresses) from db backups without ruining their integrity? If you use something with an immutable log, like Kafka, how do you remove the data there? Etc, etc
1 - google is the only company (bing to a much much lesser extent) with access to primary search data. If you believe that the original pagerank algorithm is too easy to fool and that it has been massively deprioritized in favor of gathering intent data created by user actions on google, this makes them a natural monopoly. Any other attempt to gather the data to make intent targeting work will be hindered by the lack of consumer touch points.
2 - see consumer touch points above -- very few companies have them. Eg the new eprivacy law (depending on which draft -- there are conflicts between Council / Commission / Parliament), will be a virtual monopoly guarantee for FB / Google / yahoo. One of the features is that company 1 can't ask for consent on behalf of company 2, so, again, only companies with an end-user touch point can get legitimate consent. Thus all 3rd party adtech dies. This seems in direct conflict with pro-competition rules in the EU.
3 - Adsense also becomes much harder to compete against. Google does intent extraction -- buttressed by the data from search -- better than anyone else. You can, of course, attempt to compete algorithmically, but you lack the data.
4 - GA allows to extract behavior post click from within the site. No one else has this. You don't even really need personal data for this to be amazingly useful; merely aggregate is very powerful.