Games

Honestly, even those are pretty overkill to make a competing storefront. All you'd have to do is to offer lower prices and/or take a smaller percentage while matching at least a fraction of Steam's functionality (unlike Epic) or actively working to screw over customers (also unlike Epic). If a store sold games consistantly 5% cheaper than Steam, even without controller options, good support, a built-in forum, explicit Linux support, ect., I'm confident it would be reasonably successful. Just look at Humble and Fanatical. While they do (mostly) sell Steam keys, their prices are arguably what made them a success, not the features you get after redeaming the Steam keys.

Even beside that, the ideas you provided are all pretty minor. If you're willing to throw more significant amounts of money at the platform, like many before have, you can go a lot further than that even. For example, seeing as Steam's discovery algorithm is one of the bigger benifits Steam provides, you could one-up them by providing off-platform marketing for games launching on your platform. This would be a way to bring devlopers and players alike to use your platform without screwing over either. Similarly, you could take a page out of Epic's book and do giveaways regularly. Alternatively, you could use a less generous system such as "buy anything and get x game free" or "every $10 spent gives you a chance to win x game bundle" to make it more sustainable, and/or allow you to market specific underperforming games. It isn't that hard to come up with ideas that would allow a competitor to do well. You just have to do that rather than putting all your resources into trying to take games away from players, and harvest their data.