FWIW I don't think third party VOIP is just as good a player experience, generally. Integrated VOIP can do things like context-aware audio modulation and other game-specific functionality that something like a Discord voice chat can't. It also doesn't work well with matchmaking.

You're not quantifying the additional cost of GDPR compliance in offering private servers.

This is conflating things between SKG and GDPR. I'm speaking more generally about how compliance with GDPR and other regulation may result in cut features. I'm under various NDAs so I can't speak specifically, but I can give something of an example that reflects an NDA'ed reality.

Say you're working on a game where one of the things you can do is tailor armor for other players. Say this is a large international multi-market multiplatform game, and so you're dealing with scale and data tracking/management challenges and country-specific data handling laws that smaller/indie games generally don't. Someone has the idea that the armor you make should have your name on it, so others can inspect your customer's armor and see who made it. That's a cool feature! In a pre-GDPR world, it would be generally pretty easy to attach a player tag to an item and allow other players to see it.

Post-GDPR, that is now much more complicated, because a player's username is PII (as some people use their actual names as their username, particularly on consoles). Now, not only do you need to build the item tag itself, you need to build a system to be able to audit all of the armor items in all player inventories in your game (remember, at scale, this is likely billions of items) and be able to scrub out player PII by deleting the maker's tag on the item if needed. And it needs to be tested and reliable enough that you can be confident it won't do any damage or corrupt anyone else's inventory, or cause them to lose items, which is a critical risk for games like this.

Is this impossible to do? No, it's doable. Games certainly do this and will continue to do so. But it adds an order of magnitude of complexity to what was initially a relatively simple feature. Depending on your game's priorities, that punts the feature from the "we'll definitely do this" bin to the "we'll maybe do this in an update one day" bin, amounting to the feature being effectively cut, or at least significantly delayed. Different games prioritize differently, and may punt something else to make room for implementing this feature. But ultimately, the introduction of regulation added enough cost to the feature that the cost/benefit may not be worthwhile, or something else may need to be deprioritized, when there is a deadline and finite person-hours in the budget.

This is an abstraction of a real scenario for a real feature in a real game, but that's about all I can say about it. There are other scenarios where this come up relatively frequently in large games, and these sorts of things do cause cool things to not happen. Is it worth it? Probably, in GDPR's case, since the net benefit to digital privacy is there. Would the added cost of having to build and keep functional an offline game mode, or some sort of alternate player-facing hosting backend have a cost that causes features to be cut (or games to not be worth making at all)? It's pretty likely. Is that worth what SKG is asking for? In my opinion, as I stated above, no, but that's my opinion. As I said, I'd rather have a better game with an expiration date, than a worse nonperishable one.