As much as some Mall in your city charging high rental rates. If they are not stopping other malls from being built (say by bribing politicians), and they are not stopping people from setting up solo shops, I don't see where the anti-competitive force is.
Apple's case is much different. They are using oligopoly power in one area (high share of OS), to extract revenue in other area. It's like if one of the biggest cities in the country, had a Mayor who also owned the only Mall in that city and stopped any other Malls from being built and charged super high rental rates in that Mall.
I had a quick look.
Per https://www.shacknews.com/article/130287/valve-faces-antitru... , Valve are currently (?) being investigated for Most Favored Nation practices.
This is the equivalent of a high rent mall demanding that its shops don't charge less for its wares in lower rent malls.
Steam also doesn't do exclusives (beyond Valve's own titles), nor do they pay any OEMs to pre-install Steam - with the exception of the Steam Deck, all Steam installs come from people who actively seek them out. It's not like Apple where (until recently) you had to go through them to get your app on iOS and pay them every step of the way for the privilege.
I play so few games that I'm happy to buy mostly from the much smaller gog.com. I'm not sure if their fees are less, but it at least raises competition.
I generally don't trust DRM platforms like Steam or Epic, but bravo to Tim Sweeney for championing smaller publishers unable to negotiate down from Steam's 30% fees.