A lot of times I'm watching a soccer game and a call goes to VAR. The VAR people review it for a while (and for an offsides it feels like they go down to the inch). This doesn't make sense because it is supposed to be clear and obvious but if it takes 1 or more minutes to decide it is neither of those.
The amount of time it takes to review is somewhat of a pain point with VAR. Soccer involves many people, and their interaction with each others. To review you need to look at a number of angles, and interactions are open to interpretation.
In tennis use of Hawk Eye is automatic as the only need to be tracked is the ball. But in soccer you need to take a look at the ball, on a much bigger field. As well as position of the players. But also how the players physically come into contact with one another. Many angles need to be looked which results in minutes review in many cases.
Don't forget that the VAR people have multiple cameras they need to watch (where I am, in the Netherlands, at least six); a situation may be difficult to judge from all but one angle. It takes a while to review all that footage, especially if the fragments are long (I think that a foul at the very beginning of an attack can already influence whether a goal is valid or not.)
And sometimes, even determining whether something is a clear and obvious error is rather subjective. It may not only depend on the situation itself, but also the position of the referee.
In principle, an objectively wrong decision must be a clear and obvious error, as nobody in possession of the facts (and the applicable law) could consider it to be correct.
Some reviews require a check of extreme detail to determine whether an objective fact such as offside or handball has been missed or incorrectly observed, and an incorrect decision derived from the wrong information.
if the ball did not make contact with the arm or hand, as described in Law 12, it cannot be handball (this includes where the ball has struck the shoulder above the level of the armpit, and the arm was not raised or in an unnatural position) and therefore any penalty kick awarded on that basis is incorrect.
if a player was in an offside position and has played the ball after receiving it from a teammate, as defined in Law 11, they have committed an offside offence, and therefore any goal scored must not be awarded.
In reality, the implementation of VAR was inconsistent and poorly carried out, generally leaving individual national associations to apply their own interpretations (and later be reprimanded by IFAB or allowed to continue), or to apply the interpretation "that IFAB intended" rather than the protocol actually written according to the Laws of the Game.
This has lead to exactly the criticism that VAR has been used when it should not be, with "clear and obvious" having an ambiguous and inconsistent meaning in the real world.