High Sierra support ended last November. Mojave is supported till next November. You have more support options from Apple if running a supported MacOS. Just sayin’…

In the meantime, it looks like your Mac is taking way too long to shut down. Simon’s power switch works but doesn’t fix the problem. The following should. Not only does this reset your Mac to default but also every installed app. Launch Services sometimes become corrupted during a Security Update.

Reset Launch Services

1. Open Terminal and run these commands (copy and paste) then hit Enter or Return:
2. sudo /System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -seed -lint -r -f -v -dump -domain local -domain system -domain user -domain network
(It will now ask for your Admin password)
3. killall Dock
4. sudo mdutil -E /
5. Restart your Mac

You will see many pages of commands, one set for each app. This is normal.

I first ran into this when my 2010 iMac and my wife’s 2015 MacBook Air wouldn’t shut down while attempting to run a 2019 Security Update over High Sierra—holding the Power switch was the only way to shut down. After the March 2020 Security Update, my iMac Pro would take 6 minutes to begin booting. In each case, resetting Launch Services fixed me up. Apps launch more quickly, too.

BIAB 2024 Audiophile Mac
24Core/60CoreGPU M2 MacStudioUltra/8TB/192GB Sequoia, M1 MBAir, 2012 MBP
Digital Performer11, LogicPro, Finale27/Dorico/Encore/SmartScorePro64/Notion6 /Overture5