My standard example for "GIMP is unusable" is "try to draw a straight line" which I had to find a tutorial for (you need to hold some magic keys). That said, I struggled with that in Photopea too (not realizing my intended red line was there, just hidden by the blue vector indicator).
I get that but hold shift for constraints is standard in almost every editor out there. (Not sure about Photoshop, it has weird behaviors for modifier keys.) Also, I find GIMP more intuitive for some things. For example, making solid-color backgrounds transparent is very easy in GIMP but as far as I can tell impossible in Photoshop.
I'm not talking about constraining a line to a 90 degree angle. I'm talking about "draw a single straight line from one point to another". Most editors have a dedicated tool for that. In Gimp, you take the brush, then shift-click start and end.
How do you do the solid color background in Gimp? In Photoshop, I'd select the background with the magic wand (contiguous or non-contiguous, depending on preference), potentially use one of those edge-improving tools, then either press delete or create a mask. It apparently also has a special tool for it that I haven't used before but seems to do basically that.
Oh, OK. Regarding the background: That works, and you do the same thing in GIMP but that doesn't handle transparency. In GIMP there's the Color to Alpha tool which is pretty much magic.
Say you have https://this.is-a-professional-domain.com/4Hhtqcf.jpg and you want that glow on a transparent background. In GIMP, I'd select the chip, Select>Invert, Color>Color to Alpha and it would just work. I tried to do it in Photoshop and couldn't figure it out.
Meanwhile, this kind of attitude in users is exactly why everyone is stuck with dumbed-down, more complex/more buggy, less powerful solutions. The more information is available at people's fingertips, the less people are willing to take a few seconds to discover it.
