Original room assignments are now done by an automated computer process. If I understand correctly, there really isn't a room assigner with a role like in the past. So I don't think there is anyone to make mad, and even if there was, no I don't think that's why you didn't get your request.
Everyone cannot get their requests. You've just had bad luck.
You can ask at check-in and remind the CM at the desk of your requests and see if they have been met. As to whether you can request a different room at that time, ????. I have in the past, but it seems like they are trying to crack down more on
DVC members (especially) being moved at check-in due to room requests (vs. a problem in the original room assigned).
My family has repeatedly gotten our requests when we make them - DVC or regular Disney rooms. In fact, on our 2nd Beach Club Villas stay, I mentioned at check-in how much we liked the room location we had had previously and they were able to give us the same room. But that was done by the CM at check-in. I don't do online check-in, but I do add requests to my DVC reservation if I have one.
PS - just read your post a little more closely and (despite the one experience I wrote about above), I would NEVER request a particular room #. The chances of being able to get a particular room are infinitesimally small. That is more likely why you have not been successful. You need to request the things you want in your room -not a particular room - so things like near parking, near lobby, near elevators, whatever. Those types of requests have a higher chance of happening. Don't request room numbers because if that room is not available, they will just stick you wherever.