I know it likely doesn’t help you with your installation efforts right now but I see a few things the installer does
- it spares you reading lengthy/confusing installation instructions that all sound gibberish to non-smartphone manufactures/developers (ultimately you have to use tools for smartphone manufactures/developers to flash a custom ROM)
- it spares you finding a working/not outdated tutorial in case you don’t succeed with the official install instructions
- it automatically downloads all the right files you’ll need
- it spares you the questions where/how to put/extract all the files and how to find them back
- it keeps you from spelling errors when you type the commands (“normal” users don’t know how to work with the command line and usually there’s no need for them to learn it)
- it keeps you from forgetting a crucial step or doing them in the wrong order
- it keeps a log of what was executed behind the scenes and what were the results (which would hopefully help to identify the root cause if something doesn’t work as expected or help to improve the installer itself)
- it keeps you from simply trying random stuff that makes things worse and might brick your phone
But it doesn’t (yet) solve all problems that might occur
- missing/wrong drivers on the computer
- using a charge only-cable
- pressing the right button combination at the right time on your phone
- permission problems on the computer OS
- not following the instructions correctly that need to be done before the installer can pick up and do its work (allowing USB debugging/OEM unlock)
And of course - as any software - the installer might contain bugs