Genres which are popular are well reviewed by the reviewers. However, new and rare genres like adventure, Sim Racing titles, and others are not always well received since they are new to the reviewers themselves and they cannot compare it to anything else.
How many reviewers do people think even know about sim racing in the first place? The only people who can properly review a game are the ones that have some experience with the genre, and only then can you call them as professional.
I can understand the metacritic argument, but its not always right. For eg., Heavy Rain got a lot of flack for its gameplay(lol). Its true it still stands at a good 87 on meta, but its an adventure game and I think its unfair to compare its gameplay to the action genre. They are both different.