Good or bad or neutral, FB's targeting specifically works amazingly well and better than anything else for many buyers. Especially for direct response ads.
If you can't make money selling your product from digital ads, you're not saving dollars you're losing revenue. This is true especially for 'internet only' upstart products, for example everyone who gets stuck in for instance a $60 athletic short ad loop as an example!! Sometimes you hear examples here about a new product or kickstarter who pre-this type of digital would probably not be able to launch or it would be much harder.
Brand advertising is different and targeting can definitely argue doesn't matter as much.
But these changes has already changed how we spend money, and we're tiny in the grand scheme.
The other point that always gets thrown out: It's also incredibly simple to measure effectiveness or lift.
Staying with FB as an example, if you are selling a product it can be as simple as using a unique link for your FB ads. ROI = Purchases with that link / FB spend. FB also has a large set of conversion tracking JS and offline like loading your retail conversions to the platform to match.
But given the new rules FB is now 'modeling' ROAS and it has decreased accuracy for us from something like previously capturing 80-95% of conversions to sometimes less than half. This makes a big difference in auto-optimizing on their end and thus our ROAS.
And again sure, it gets complicated and definitely more snake oil to buy some 3rd party ad tech which claims to model across all your channels online and off. A lot of times that's gamed or just a bunch of BS.
But another way to measure is say you're a larger brand buying TV, digital, OOH etc the works. You can simply control by making only one single change segregated to a control and treatment geo/group before and after, measure delta.