It doesn't as a monopoly isn't inherently something bad. We generally just assume so, because of the negativity and strong regulation attached to it.
https://www.economicshelp.org/microessays/markets/advantages-monopoly/
That's where ethics enter in the whole conversation, because monopolies are obviously easily exploited
(And were so for a long time in a lot of countries) The act of HOW you conduct your business. And at least on that front Epics actions are... questionable for a variety of reasons to a lot of people. I
That said. A lot of those questions arose from how Epic approached the whole thing, they can still right the ship even if it takes some time. Expanding on resellers, providing services, declaring exclusives in advance (even better focusing on supporting indies with said money),,,,,
Sadly, at the moment its a hate mob where its two front were getting more extrem by the minute. So, while I personally also boycott the Epic Store (mainly due to their approach to PR/customer second) I do hope the Epic Store works out as it should have been.