One of the big problems is that the tags are meant to describe current content and not future content (an F95 rule apparently), so a dev may have the intention to add certain kinks/fetishes, but they aren't in the game/VN yet. Tags may subsequently be forgotten to be added when that content is eventually added. But ultimately it's hard to determine the direction of the game/VN from tags alone (that's why it's always helpful when there's the "planned content" section in genre).
As you've mentioned. Sometimes the tag is there purely due to a mere reference, dream sequence, etc.
Another big problem is that tags aren't all telling. A game/VN may have the NTR tag (or any other kink/fetish tag), but dependent on the game/VN, it could either be avoidable or unavoidable. Another set of tags that can be misleading is when a game/VN is tagged with both male and female protag and multiple protag tags. This can mean different things:
1. You choose at the start of the game/VN if you want to play as a male or female protag and/or different looking protags and that's it
2. During the game/VN the identity and/or sex of the protag will change (some people aren't fond of female protag games/VN's unless it's a fully lesbian affair)
Basically, there's a lot of areas for potential confusion and frustration. It's just a matter of the attitude somebody uses when asking or making criticisms. Some are clearly very hostile, while others not so much, so they should be treated accordingly.
