I'm on Windows and running into the same issue with Cura becoming unusable after it has been running for a while. It seems that if I reboot my computer, Cura will be snappy again, but the longer I go without rebooting, the slower Cura gets, regardless of whether of not it was open the whole time. I have tried disabling the same suggested plugins, but it does not seem to help. I also did a reinstall today, and after restoring my backup, Cura became slow again, so I am wondering if there is something about my config files causing thins.