I'm pretty sure Fortnite Battle Royale was released in late 2017. I don't know what are the cut-off dates to consider a game as a 2018 GOTY contender, though.
My GOTY would be WarioWare Gold followed by Taiko no Tatsujin but I don't work in a gaming outlet so my preferences are inconsequential in the grand scheme of things.
Sure. So, technically, we might have new versions of Tetris Effect as GOTY 2019, 2020 and so on as long as Eurogamer journalists think those are the best games of the respective year?
Tetris Effect isn't a re-release of Tetris, though. It's a new take on it. So it qualifies. A re-release in a GOTY pack wouldn't work since it would be genuinely the same game.
There's nothing wrong with your opinions. If you were doing a GOTY list of your own for a major outlet I would expect you to choose those games. What good would such a list be otherwise? I made my own video on my Games of the Year based entirely on what I enjoyed most. Nothing more, nothing less. If your decision is influenced due to status of the site then it wouldn't useful or interesting.
There is no objective best game, after all. It's all subjective.
As for Fortnite, hey, I'm with you. I don't like it at all would be happy if it disappeared forever. I would never have included it on a 2018 list.
My point about 'new' mechanics is centered around the fact that I see more value in refining ideas as opposed to always trying to innovate. Taking an existing concept and perfecting it tends to lead to the most memorable games for me.