Mainly electron itself. For example the discord app (which uses electron) is less memory efficient (and much more restrictive etc.) than just a separate Firefox instance. It also had many problems with being up to date, but that's due to the discord devs deciding they want an own, custom electron, based on an outdated version. The main problem with electron for me stems from the chromium base, as basically any large app based on chromium (discord, spotify and steam) has massive flickering and performance problems on Wayland+Nvidia. A special combination, but still a factor for a 'cross platform' framework.

On the other hand, stuff like Signal never had any problems on my machine.

So, just use the stock electron, optimally the system one [electron binary], and see if you can enable wayland compatibility natively (otherwise we need to use environment variables etc., which works moderately at best).