I don't mind someone going after Valve but I think the arguments presented are bullshit.

The price parity argument is an argument on paper but in reality we're not going to see different pricing, except maybe on the super rare occasion a company has their own storefront they want to build up with their first party games while also keeping the game on Steam for extra sales. Realistically that first party game is going to be exclusive to the store (see Alan Wake 2). And 3rd party publishers have no incentive to sell for cheaper on a different storefront because a lower cut by the platform holder would just mean they get to make more money per unit sold. I guess maybe if the storefront pays the 3rd party publisher extra so the storefront itself could set a lower price on the games, but I fear that might end up having the opposite effect where money-rich competitors (like Epic) can end up taking away market from smaller storefronts like GOG or Itch because despite selling games for less it's still not competing with Steam in terms of features so the market has to grow from somewhere. But I'll happily be wrong here.

The same way the 30% cut being too much is an argument on paper, but in reality if the cut does go lower the customer, the people actually buying the game, won't see it. One could argue that it has already gone down for AAA because Steam brings it's down to 25% after certain threshold and I think once more to 20% after the next threshold. Meanwhile AAA pricing has only gone up in the form heavier focus on MTX alongside an actual price increase from $60 to $70. The cut going down is just going to put that money in the publishers pocket. It would be a win for the publisher but not really a win for the customer.

The only argument that actually could be beneficial to the customer is the add-on argument. I'm not entirely sure what they mean by add-ons. If they mean Steams own made up marketplace of trading cards and stickers and all that shit what is the solution here? Have Steam close it down because there's no way in world other storefronts would ever make something like that and if they did it would never be made in a way where it could be interchangeable with Steams implementation. I hope by add-ons they mean DLC-s and I would 100% love it if I could buy a game on one platform and DLC-s from a different platform and just have them work together. That would actually be beneficial to the customer. But I don't see anyone codifying that as a regulation and if it were to happen it would be pretty big strain either on the storefronts or the publishers, because it would be a huge mess to track purchase across platforms to make sure what combination of games + DLCs any particular account has. I would love to see it happen, I just don't see it actually happening.

The arguments are there on paper but even if Steam did anything about them it probably would have little to no effect on the customers so the lawsuit doesn't really feel like someone is fighting for the consumer, it just feel like someone trying to take Steam down a peg. It's fine but it's unlikely to have an impact on the market, Steam will still stay the biggest seller because Steam offers features to the consumer that no other storefront offers.