I agree, but I think it's important to consider that they can succeed even if they don't get you or me. There's hundreds of millions of people that have installed it (approaching 250 million a couple months ago), tens of millions playing each month (almost 80 million as of a few months ago) and over 10 million people playing concurrently.[1]
How many of those are young players that might want to try a new game they see some youtuber play, and see it on sale in the epic store they might use to launch Fortnite? That's a hige captive audience, and this battle won't be won by swaying you or me, but by swaying the huge number of new gamers coming onto the market, which are mostly our kids. I know my son who's 9 probably wouldn't care about Steam if I wasn't sharing my library with him. Then again, his computer can't play much and he plays Fortnite on the Switch.
Steam is entrenched, and does have it's own user base, but given that Fortnite along as of a couple months ago has ~66% of the concurrent users of Steam overall[2], I wouldn't count it out. That's a lot for Epic to make something out of.
1: https://www.pcgamesn.com/fortnite/fortnite-battle-royale-pla...