If you have an ARM device (e.g. M1 Mac), make sure to install the ARM version (https://github.com/laurent22/joplin/releases/download/v3.3.9/Joplin-3.3.9-arm64.DMG)
See: Joplin offer to install raw 3.3.9 version on MacOS - #8 by sinewave-2097, there's a bug where it's installing the x86_64 version on ARM devices, which causes slowness due to rosetta translation being used