Third party client support. Specifically alternate web UI’s focused on desktop like Alexandrite because if I’m being honest here, I think the comment nesting in Lemmy’s offical web UI lacks enough distinction to be useful on desktop (its clearly optimized for mobile browsers). Following conversations can be frustrating on desktop. Without Alexandrite I’d most likely be a mobile app (Voyager) user only.
Edit: No, third party web front ends for reddit do not work anymore. Remember those pesky API changes that went into effect in July and were the entire reason the majority of us are on lemmy now? Yeah, that didn’t just kill off third party mobile apps.