It been downhill since they went Electron, I don't remember the old app taking more than 3 to 4 seconds. Since the Electron client loading times have been unpredictable sometimes 5-10 seconds and sometimes to around 30 seconds even though no updates available.

Edit: CEF

Yeah Steam is cool and all but this is not its strong suit. It is rather hilarious to see every other app on my CachyOS install launch in the blink of an eye, and then Steam is really no different than it was on Windows.