http://upload-cdn.pixelmator.com/Screen-Recording-2022-06-16-at-15.06.43.mp4
Imagine I want to make all 5 ovals look exactly the same as the top oval. To do that, I will have to:
- copy styles
- paste styles
- copy effects
- paste effects
- take a look at layer blend mode
- manually set blend mode
That's 6 actions! And with Adjustments, it'd be 8.
I personally would find "Copy/Paste all properties" (including blend mode) much more useful. (Similar to Figma's Cmd-Opt-C / Cmd-Opt-V)
And if users do want partial copy/paste of properties, why not allow them copy/paste separate effects/styles/adjustments? For inspiration, here is how Figma does it:
http://upload-cdn.pixelmator.com/Screen-Recording-2022-06-16-at-15.20.44.mp4
Each property is selectable, I can copy it and then paste into other layers (with same Cmd-V shortcut).