to disagree slightly: there were many different stores and lunchers before Epic even existed. Apart from Steam I have bought games and other digital goods on Gog, Humble and the now- extinct Desura. While totally avoiding the stores from companies as Ubi or Ea because they just suck.
Having an addititional account wasn't the big issue. There were already attemts to integrade several libs into one launcher, and if not you can at least run the start commands for that games out of steam.
What was sucking from the beginning was that arrogance of this sweeny guy, his promises of hot air, and his telling us of being the great saviour for all developers - while we as paying custemers were fed up with this bad launcher that is still missing every user interaction.
In the end not even the developers have profited from the store. Sales are not as promised, and in order to release a game on this platform sweeny blackmails you to give away older titles for free.