I don't find scrolling left and right with the mousewheel that ridiculous, really. It's no more ridiculous than using the mouse wheel to zoom or change volume, in my opinion, but to each his own. In any case that's hardly a matter of forcing touchscreen gestures on mouse users, since it's explicity using a mouse-only feature. If scrolling was achieved by dragging the cursor left and right, I'd agree that that's a case of forcing touch gestures onto mouse users, but that's not what's happening.
I don't really understand what you mean with the other ones. I don't swipe from the left to switch apps. I bring up the app list with the hot corner and then drag and drop the app images. I'm not sure how you're doing it based on your description. Also, I have no idea what this swiping away from corners gesture is supposed to achieve, because nothing happens when I try it.
They're not all regular swipes or what people used to call gestures. It's just reaching all the way into corners then moving down like in the charms bar and the app switcher (or whatever you want to call it) which I know is really just a vertical menu with little icons so I'm fine with that one. Grabbing the top and pulling down is definitely a touchscreen thing and doesn't feel right at all. Being in a fullscreen start menu replacement just feels constraining too.
Getting your mouse into the exact right place in the top right corner with 2 monitors can be very difficult too.
I've seen people swipe from the left to the center to switch open apps before. Doesn't it work with a mouse? I believe did it back when my Win8 install still worked.
None of it is obvious either (even shutdown is hard to find), but like I said, it's fine on a touchscreen device that you're not going to run standard desktop apps on but it's just not right with a mouse and non tablet software.
It's hard to explain but people obviously don't feel right using it and it's not just because it's unfarmiliar. That's why someting like a Taskfore site is good. It will show what a bunch of us feel is most important to fix.