[CentOS] Extreme frustration with GIMP

I am not a graphics person. Also can't afford to hire one.

Trying to follow instructions at https://docs.gimp.org/en/gimp-tutorial-quickie-separate.html

I use the "intelligent scissors" just like they say, spend quite a bit of effort doing so.

Then click the foreground select tool - just like they say - and suddenly everything I did with the intelligent tool is undone.

WTF?

Does anyone know of an actual GIMP tutorial for removing background that doesn't cause me to throw a damn brick through my monitor?

Photoshop makes it easy, but clearly GIMP developers have a completely different philosophy on how a graphics tool should work and I can't figure out what their philosophy is.