As someone who used to be vehemently anti-lemmy, it's a few different reasons.

1. It's something new. Honestly is as simple as that. Most redditors are straight up threatened by new features, new looks, new anything. New Reddit is an example of that. To be fair it is hideous but it's also drastically underused according to reddits own metrics. This just stays consistently with everything. People prefer old subs to new, prefer old users to new, old memes to new. Why? Dunno. Could be as simple as just that they know it so it's comforting.

2. The propaganda that reddit put up against Lemmy was pretty insane. The first few mini-migrations set people up with weird expectations and a lot of them bounced back to reddit with weird notions. Some of it was based on shitty admins or shitty servers (cough lemmy.ml cough) but other things seemed to be almost coordinated against Lemmy. By the time that the big migration from Reddit killing off third party apps/API use a lot of people had heard one or two things and just started spreading it. Redditors often don't source material and just kinda spread rumors or 'feelings' or upvote one idiot who seems like he knows what he's talking about while blatantly lying. This has never gone away. The same idiots keep whining and being dismissive.

3. Redditors are hateful. Not purely hateful people or anything but the atmosphere encourages hate and division. I still browse reddit occasionally and I'll check the comments out about a post. It's always so bitter and angry, snapping out at one another. When every crab in the bucket is pulling you down, you get stuck in that habit too. Until you break free of reddit you don't realize just how bitter it's making you. Lemmy doesn't have those vibes and it can be really off putting to someone still in that bitterness. Kindness and people getting along almost comes off as stupid and naive so you just kinda dismiss the entirety of Lemmy as a whole.

4. This is a conspiracy but I'm positive that Reddit admins are purging a lot of references to Lemmy that don't show the site in a positive light. When the API shit was happening people kept pointing out that certain communities that were supportive of Lemmy suddenly got locked behind a NSFW curtain that forced users to be logged in to read the community. A lot of people talked about how certain posts and stuff were being removed, especially ones critical of Spez. I don't think they stopped that campaign and I think they still try to demonize the hell out of Lemmy. Could be because China has a significant hand in reddit now or it could be because Spez has a tiny dick and a tinier ego. Dunno. But I think they're weighting the scales.

Yes, some instances are problematic, yes, some devs might have had problematic views.

I mean that's basically the crux of it. That, and some moderation drama, and the software being very buggy a year ago giving people a bad first impression, and Lemmy still being susceptible to spam.

It'll take some time before Lemmy (and the Threadiverse as a whole) improves its reputation and moves on from the "it's a tankie website" take. That said, a lot of people in that thread are making the case for Lemmy, so it's mostly just people worried it's not as popular.

Lemmy has a toxic puddle problem. If your first experience with Lemmy is sauntering into a community and getting chased out for not agreeing with someone hard enough, something like that, you'll probably just go back to Reddit and say 'that place is full of whack jobs'.

And the default sort, kinda hard to dodge

Number 1 comment is

Reddit ain't going anywhere fast.

If r/selfhosted has to rely on reddit as it can't be fucked selfhosting, what chance do other subs have.

I have found Lemmy selfhosted communities excellent, they are not a large as Reddit but there are plenty knowledgeable people, often seflhosting their own little reddit.

Devs are allegedly Marxist-Leninists.

Redditors dont understand that devs dont exactly have full control of open source software, that different instances are not operated by the devs.

Edit: Lemmy devs to be specific

Sunk Cost Fallacy

Almost everyone in the linked Reddit post seems to be supportive of Lemmy, or even Lemmy users. Even the people who tried it and stopped seem generally warm to the idea and just think it needs polish.

I'd say that this comment section is way more vitriolic than that one lol

We are having a great time over here in the Fediverse, and they are jealous. So we will continue to have a blast, just to piss them off.

Doesn't !selfhosted@lemmy.world have like 40k subscribers? Top ten Lemmy community by sub count, iirc.

Besides other factors mentioned in this thread, there's also

• selection bias: people with a positive view of Lemmy already migrated, so the leftover is bound to have more negative views
• older userbase: older people use language in a different way, talk about different topics, and dig into those topics in a different way. That often makes younger people throw a tantrum.
• group identity: for those "AS A SNOO" we're basically apostates.
• edit: personal drama between higher ups is more visible here than in Reddit.

Because people off Reddit hate everything that its not reddit

No idea, quit Reddit over a year ago for fedia/lemmy. Never used x/twitter either, i use mastodon.

we are like their penal colony in revolt, maybe

Seems to me most people in that thread seems relatively open minded? The people dismissing Lemmy completely appears to be downvoted, and people seem to have a nuanced understanding that it's a better platform in theory but sadly less active.

I'm sure they're right. I'm a slow person who thinks there's plenty of activity over here, but if you're used to the adrenaline of Reddit it must feel a little small town-y.

Main reason is people are too lazy to change their ways and don’t want to feel like they’ve been making the wrong choice all along.

The feel of Lemmy communities is a little different than Reddit, even if the software features are mostly analogous and there are many Redditisms used.

Your average commentor/poster will stand out more in a small community, there's less of being able to post and then slink away.

People have gotten used to a lot more comforting features of modern Reddit, Lemmy in both the users and in the software has more of a "Reddit 10-15 years ago" feel to it.