No it is not. It depends on the codebase - if it is something relatively new, a proof of concept or something that is bound to change soon, there is no point in slowing the development down just because it is "too large to digest".
If you're just rubber-stamping in code reviews, why even have them in the first place in that case? They aren't exactly providing you with any mileage at that point.
Sure but who's got time for all that aggravation? Especially if it's not part of the codebase I have to work with personally. LGTM and let it be someone else's problem.