Upvoting isn't about whether you "like" something, it's about whether you think a question/answer is good. In the case of this site, a good answer is "useful and appropriate", and will provide lasting value for a variety of users, but what constitutes a good answer will change from site to site.
I think the issue here is that you're complicating the concept of voting by thinking of it in questions like "Do I like/dislike this?", rather than "Do I think this good?" or "Do I think it provides value in the context of this site?"
Sites usually make an attempt to clarify what this means:
Voting up is how the community indicates which questions and answers
are most useful and appropriate. Whenever you encounter a question,
answer or comment that you feel is especially useful, vote it up! - Source
"If you think something contributes to conversation, upvote it. If you
think it does not contribute to the subreddit it is posted in or is
off-topic in a particular community, downvote it. - Source
Only two examples, but both present voting in way that has nothing to do with like and dislike. There may be some overlap between things you think are "off-topic" or "inappropriate", and things you don't "like", but it's just overlap.