Synopses tell you what's the anime/work about, usually with a bit what makes it good. Like most things, you have to find out for yourself whether or not it is.
So either way, you'll be spending time assessing it. Now if you really want to know whether or not an anime is good or bad without watching it first, you ask people/read reviews. But people may not have the same taste as you, so depending on how interested you are, you still end up looking at it yourself.
Really, the only way for you and me to determine whether or not an anime is good is to watch it ourselves. You have your own criteria and I have mine, and Aki has his. Personally, going in blind just saves me the trouble of having people tell me their biased opinion about the anime.
So either way, you'll be spending time assessing it. Now if you really want to know whether or not an anime is good or bad without watching it first, you ask people/read reviews. But people may not have the same taste as you, so depending on how interested you are, you still end up looking at it yourself.
Really, the only way for you and me to determine whether or not an anime is good is to watch it ourselves. You have your own criteria and I have mine, and Aki has his. Personally, going in blind just saves me the trouble of having people tell me their biased opinion about the anime.