I don't really care about the updates for better or worse, but do wonder why they keep making them?
Why do anything if no one asks you to?
why do they keep changing how it looks instead of adding something useful
Because things need to have a fresh look to avoid going out of date? If they didn't constantly update how it looked, it'd look like this still:

Also, DrenDran, the internet is a fast-paced organism that's changing by the day. It requires a lot of work to keep at the edge of that and not fall behind. Sites that fail to adapt end up like MySpace.
I hate the stuff out of the HTML5 player in general thanks to the fact there's no way to opt out of using it dammit.
Why would you want to opt out? The HTML5 player is faster, integrates better with your browser, and has more features. Flash technology is old and most sites only support it as legacy nowadays.
why don't they make it so that the theater mode player actually makes the loving video bigger instead of just centering it and putting a black box around it
It depends on the maximum resolution of the video. It does actually make it bigger, as long as there's a resolution to match.