Wow, the update to the UI takes this problem and makes it even worse.
It used to be that you could initiate a new game using the new game button in the lower right under the move list. Now that's been removed, so the only way to start a new game is using the jumpy dialog box that covers the board and moves the new game button out from under your mouse cursor when you try to click it.
:-(
When a game is finished, the end-of-game dialog pops up. There are two reasons it's bad.
1. It blocks a big chunk of the board. The first thing most people are interested in is the final state of the game. If I don't want to go to Game Review and just see the final position before going on to my next game, which I'm guessing is the situation for most games, blocking a big chunk of the middle of the board is bad UX.
2. The buttons jump around. It is maddening when playing a bunch of bullet games to go to click for the next game and then have the Game Review button sneak under the mouse cursor when trying to click New Game. A dialog should never jump around as bits of the UI load, just put the dialog up with blank spaces for all the info to load into. (I'm actually shocked that someone needs to point this out, chess.com is a mature site and this is UX 101 stuff.)