This very post showcases one of the ways it's crappy.

Centralised control inevitably leads to enshittification (lemmy isn't immune to that either, but at least the damage will be contained to a single instance; the only way to avoid that is a fully distributed service, or at least the ability to fork communities with their whole comment history like you would a git repository).

More importantly, though, while it might be passable as a chat app if it weren't for the aforementioned centralisation bullshit (though IRC was completely fine in that regard and there's no need to reinvent the wheel, much less to put a clamp on it), it's being used to replace forums and wikis despite not being designed to or adequate for the job, locking up information that should be freely accessible and searchable into an unsearchable account-locked black hole, violating the founding principles of the world wide web and becoming a parasitic cancerous growth upon it. When a seemingly interesting project tells me to go fuck myself, sorry, to go to their discord for information instead of pointing me to their forum or wiki or even FAQ page, what I'm reading is that they couldn't give less of a flying fuck about their users, that they'll embrace enshittification as soon as possible, and that I should look for a better alternative.

Also, as others have already pointed out, it's a web page wrapped in electron bloatware. If you're embarrassed that your “app” is merely a web page, either deal with it, close it, or make a proper native app, but hiding it under a locked down browser in a trenchcoat doesn't make you any favours, it just highlights how little you think of your users, which just corroborates the previous points.

TL;DR: It's malware all the way through, and was always designed to be, and it's actively harmful to a free web. Kill it with fire.