I think the "fanboyism" of Steam is a bit different to platform wars like PS vs Xbox, etc.
Fundamentally Valve has built up a lot of trust with the gaming community, and other than microtransactions and gambling, I think it's very fair to say they've been a net good for both the PC gaming community; as well as the ecosystem.
Proton is a great example.
Valve have my trust just by being privately held company that can actually plan for decades ahead instead of try to appease major shareholders or black rock.
It took them 10 years to make Linux a competetive gaming platform.
They invested in VR early and still do a lot for this niche market.
They brought back hanfheld PC from being niche chinese devices to being mainstrean and maintain support for Steam Deck for 5 years.
As game developer I do find 30% cut abysmal, but it's not any worse than consoles and I dont like Epic as a gamer for being awfully anti-consumer. I certainly dont want PC game market to be controlled by chinese Tencent subsidiaries.