Reviews are snapshots, but few people treat them that way. The fact is, restaurants are performance art - like theater, music or dance, except with an unlimited run. Your dining experience depends not only on the menu, but on the cast - who's in the kitchen, who's serving, who's hosting, etc. Despite the fact I go at least twice to each restaurant and sample as much as possible, it's a snapshot. This is why I don't list stars in the dining guide, a list of restaurants I've chosen for various reasons and which we keep as current as possible.
Star ratings are temporal things.
It's very difficult to keep up with shifts in restaurants' menus and hours. It's impossible, in my opinion, to keep a star rating accurate over the long term. Stars and headlines stick in readers' minds long after the review description has faded. Sanitation ratings are snapshots, too. Yes, without question, they are an indicator of cleanliness and worth.