While I have not tried the electron version, I feel that my seven slack tabs slow down my firefox noticeably. Especially during startup and after connectivity issues.
While the mobile app is at least responsive on Android, I have problems, too, for example with messages from push notifications that don't show up when opening them.
Subjectively, Slack performed great in the early days but has gotten worse over time.
I don't think serving local content would explain why the desktop app insists on munching through all the available RAM (on a single team, no less!), something else must be going on. But that's actually a pretty good suggestion - I'll try the web version, thanks.
While the mobile app is at least responsive on Android, I have problems, too, for example with messages from push notifications that don't show up when opening them.
Subjectively, Slack performed great in the early days but has gotten worse over time.