I found good questions about this subject (like that one) but they weren't quite narrowing to what I wanted to ask. So I wrote my own.
I have been reviewing for a few months now (~725 reviews) in those two sections (Late Answers and First Posts) and I have seen so many upvote on question that doesn't really deserved it. (e.g. Here and here)
In those case, I was almost angry about the reviewers that upvote them, feeling that they didn't took anytime to understand what's the question, which answers are already there, is the question already solved, how much the post they are reviewing is adding value to the thread, etc.
It happens often and during I'm reviewing posts. I'm still reading through and suddenly 1 then 2 and even 3 upvotes in a row.
I think some user don't put enough time in a review, maybe the Upvote option is so easy or at some point they don't really bother to read it entirely and they just want to get their daily cap.
In depth analysis of the situation
Maybe they don't understand the impact of a bad review on the community on the long term. The thing is those First Posts and Late Answers are the best way to educate new users to SO (or any other) and explain them how it works.
If people just up-vote them quickly without putting enough time evaluating which action would be best, we will lose the opportunity to show to those new users how it works.
When they got upvote 2-3 times for a bad answer, for instance, they will think it's the way to write them. They will come back later posting similar bad answer elsewhere. However, that time the reviewing system won't catch it!
I know there is a limit on the number of posts you can review per day. There is also if you reached your daily vote limit. Both helps, but I don't find it enough to prevent those kind of bad reviews.
I thought about few things, but I'd like to know what other people think about this.
Limit the number of Upvote in the context of a review
For example, if you are allowed to review 20 Late Answer and 20 First Post a day, you have a limit of 10 Upvotes. Think about it, how many times half the reviewing post will really deserve an upvote? You're are lucky if you got 3 in a row IMO.
Find a way informs users how to perform a better review
Maybe there is not enough emphasis about how to make a good review? The first time they access the Review system, we could show them a page to teach them what is a good and a bad review.
Increase the reputation needed to make those review to 500
It honestly took me a little while to understand a lot of aspects of the system : what is the mentality when reviewing, what should be done. I often had questions myself and I went on Meta reading threads to know what should I do in some cases. For instance, when the answer is very similar to another one, which flag I should use, etc.
I don't think a lot of people actually do that. That's why I think there should be a lower limit of 500 rep, so users have enough experience to make proper review. Because even though they are the first type of review users can do, they are important IMO.
I don't want to target anyone, but this enforce my point. I have seen users (member since 2-3 months) with more than 2000 reviews done in total and they have literately ~1 500 vote cast where only ~10 are voted down. I highly doubt that so many reviewed posts were good enough to be up-voted. The saddest part of this, is that even with a limit of 1k rep (as suggested by Kevin), some of them would not be affected by that limit.