Zulip is working on having public view of streams without having an account. It's already being experimently deployed on the Zulip Dev's server.So that should make its way to other consumer servers soon!
I had created this extension for my personal use, that "modernizes" the Zulip UI. Most people seem to have a better UI experience using it from the feedback I have received. Feel free to try it out .
https://addons.mozilla.org/en-US/firefox/addon/prettier-zuli...
Zulip desktop is working to move from a electron's webview to Browserview. Slack has completed that migration and seems to have received a good control on its memory usage after that. Hopefully, once Zulip migrates it stops being a resource hog.