How is anyone going to compete with a platform that most gamers have all of their games on?
They could offer their games DRM-free, guarantee that their multiplayer games have LAN or provide servers and/or at least provide that information clearly to the consumer, write an open source drop-in replacement for Steam Input and Workshop, guarantee more uptime on their matchmaking/friends servers, retain old versions of games that they distribute, and allow for user-customized or open source clients to fit all sorts of UI preferences, off the top of my head.
GOG mandates that all games must be DRM-free, so when I shop there, I know what I'm getting. Valve has tags that tell me if a game supports LAN, but developers aren't required to report that, so I can't tell if a multiplayer game I'm buying is built to last if the developer didn't think to list it; if they were required to, that would be different. People lean on Steam Input and Workshop because those features are made easy for them, but using them means you don't get those benefits outside of Steam, so there should be an open, third party alternative that developers can easily switch to if they're familiar with developing for Steam; a company running a non-Steam store has an incentive to develop this. Matchmaking and friends servers, as they exist today, are frequently provided by the storefront, so when Steam servers go down for maintenance and I'm in the middle of an online match of Skullgirls, we get disconnected, and we have to wait until they come back up; there are ways to increase uptime and prevent this interruption, but Valve hasn't improved the situation in at least 15 years.
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.
If EGS mandated those things it would be as successful as GOG. Which is irrelevant compared to Steam. Steam didn't become successful because of tags. It's because they were first.
GOG succeeds in one key area that gives me a reason to shop there. Steam succeeds in other areas. Epic succeeds in none. If GOG wants to supplant Steam, they need to be good in that key area and the areas that I value from Steam. If Epic wants to supplant Steam, they need to give a single shit about what their customers want.