I'll gladly chime in on this. I work in the industry and own my own publication. I, myself have written many reviews for several big AAA publishers including EA, Activision, Microsoft, Ubisoft and so on.
I've reviewed many types of games ranging from the recent massive games such as Assassin's Creed Valhalla for both old gen and new gen.
Call of Duty: Black Ops III, Call of Duty: Black Ops Cold War
Dark Souls III Ringed City
Those are just very very few examples of games I've reviewed personally, while others have reviewed titles such as Sekiro, Division 2 etc...
Anyways.. in regards to length and finishing games that depends on what the game is and when you are given a copy. There have been times when the publisher hooked us up on the day off release (which is unfortunate, because you lose the hot window for clicks and embargo lifts) and there have been times where a publisher have given us over 8 days. For example games like Halo 5 Guardians was recieved upon almost 10 days prior to its release date. So it was a lot easier to play all of the game's content on top having enough time to sink in to the point to where you may form a solid objective opinion.
The issue is with most day game reviewers is that they focus on silly things such as politics or unrelated topics that don't tell the main points of the game such as the actual gameplay feel, technical prowess, bugs/glitches and most importantly whether the game is fun or not and provides enough entertainment value for the amount of money you pay.
Me personally, I look at games differently depending on their price tag, if a game is $30 i will make sure to have an objective mind on whether the game is worth the $30 or not for what its trying to achieve and provide versus a game that's $60 and assuming it has more or less content.
Another thing you have to look at is the game's intended game design and if you understand what the game is trying to do, you then have to evaluate whether it does its job well.
Resident Evil 7 is a good example of that. It's a game that intentially keeps exact same core old school resident evil mechanics such as puzzle solving and roaming around spooky areas. But its new camera angle going into first person created to create a more immersive horror experience and it also opened up a new possibly for VR as well. A 3rd person VR game will never be as imerssive as a 1st person game for the obvious reasons.
So in RE7 case, we have to ask ourselves - Is the camera change working? How does the world now feel? Is it more spooky or less? Does it still feel like I am playing a Resident Evil game? Do the puzzles feel similar to old RE games? Do we feel the same pressure from the new Tyrant variant when we're in 1st person or is it even more stressful and scary?
Truth be told, its near impossible to have a perfect person reviewing every single game. Simply because us as individuals have different beliefs, feels and opinions based on our previous experiences.
Also, the rule I run down in my publication is that my reviewers will only get the game if they A) have enough knowledge and experience in a particular genre B) If they love a particular series and want to review the remake or a sequel C) Prefer Multiplayer over Single player titles or vice versa.
Basically, I never give a review copy to a person if I believe they do not have the knowledge or understanding to review such a game or if they are are just not into it. I will never let a person review a game that's like Dark Souls if they do not enjoy it or don't understand its game design. Because then you end up with a review and it looks and read poorly because the person has no clue what his talking about. That's another issue with most reviewing websites, everyone and their mom reviewed everything despite them having a lack of previous experience and so on.
I hope this shines a bit more light on the behind the scenes. Sadly, the way I run things is very strict, but its because I care about websites reputation and want to provide best quality article/review. Most sites will never do that, majority of the people writing are nothing but disposable monkeys that are being used to push leftists ideologies in the gaming industry, create drama and drive their website clicks while being paid very poorly on top of that.
This is what's REALLY happening. It's not the old days anymore, where a game gets reviewed for what it is and whether its good or bad. However, thankfully a lot of our readers are super grateful and enjoy the content simply because we keep it what id like to call "Gaming and Gaming Only."
Reviewing Valhallnwas a very challenging, we recieved it only a few days prior to its release date.
I was really enjoying the game and wanted to take my time but also did not want to miss embargo. So I had to pick my battles and play until I feet I had enough experience to make my final judgment. Unfrotuantely, we don't always get to choose how much time we get to review long titles.