You can configure a window resize hotkey. I use Win+(drag the window with right mouse) and it resizes it i the way you expect, moving the corner closest to the cursor. Left click would move the window instead of resizing.

This is by far my favorite way to resize and I don't know why it's not an industry standard.

I have deleted all window decorations and use F... keys to manipulate resize/move. But you could totally increase the height instead of deleting them

I learned to grab to resize windows in XFCE from upper right corner exactly because of this

Should be easy to correct the default behavior for the next release if the issue is reported.

It is configurable by theme or by changing something like bottom-active.xpm size.

alt-rightclick anywhere in the vague vicinity of a corner and you've grabbed it.