The reason people hate Epic is fairly obvious – they don’t give a shit about the gaming industry nor about players.
What do you mean by that? For developers, they take a much smaller fee than Steam or GOG, and for players they're constantly giving away free games.
At some point their client contained literal spyware.
That sounds like a decent reason to campaign against them. I haven't heard anything about that before. What was the story behind that? (As in, when / why / how / what? Perhaps you have a link or something.)
brute force market share via sleazy exclusivity contracts
I've heard people talk a lot about exclusivity contracts... but can you name even a single game that has such a contract? When people have discussed this the past, the relevant developers basically said "there is no contract". But maybe there is some different case I don't know about. In any case, that personally doesn't bother me anyway. If some developer wants to take money to be on one store rather than another, they can do that at their own peril. As for customers, we're only talking about a store. It's not like anyone is in danger of not being able to buy / play their favourite games. So it seems like a bit of a nothing-burger to me. Like, is there actually something bad happening here? Or are people just speculating that something bad might one-day happen if Epic got bigger?
their software doesn’t have one tenth of the features Steam has,
Steam has more features, yeah. Steam is very good. But Steam has been around for some 20 years. It's hard to catch up with that so quickly. In any case, although missing features is a good reason to prefer Steam, it certainly isn't a reason to campaign against Epic.
... So from your list, I'll keep the spyware thing and the CEO complaint. I don't know enough about either of those to say much though. I don't recall who the CEO of Epic is right now, so I won't say whether or not I think that's a good reason. And the spyware... I take that kind of stuff seriously. Right now I'm posting this from Linux - because I'm fed-up with Windows spyware. But as I said, I've not heard any details about any Epic spyware thing.
Incidentally, I've found that Steam is very good for Linux gaming. ... But obviously that doesn't mean that I'm going to start making posts trash-talking Epic. I don't find it weird that people prefer Steam. I just find it weird that people put so much energy into attacking Epic.