While some keywords are definitely iffy or totally off, most of them are actually fairly helpful in my experience. Honestly, I really don't get it when people go around saying that you don't learn the meaning of stuff when you do RTK.
For instance, I've reached the 4k mark with Core 6k fairly recently. Lately, I feel several of the new words I learn are at the very least somewhat related to the keywords I learned, if not fairly predictable. In my reviews, there's always a word here and there that makes me feel like I don't really know it... but because I'm used to those kanji readings, I can safely get the pronunciation right, and by looking at the kanji I get a pretty good idea of what the word means. If anything, it's actually annoying when a new word is one of the few cases where my knowledge of kanji doesn't help understand the meaning at all. It's definitely noticeable.
Even if a kanji has more than one meaning which you may not have learned with RTK, it's not like you have to learn all of them right away anyway. I do fail to remember keywords all the time, but it's not just the keywords. Your stories can usually help you remember a little bit of the nuance. Sometimes, you can't remember either, but have a good idea what that kanji means anyway. Another thing that I do sometimes is look up the meaning of the kanji and read my story again briefly (if I feel the need and can't remember) depending on the word I'm learning.
There's also the advantage of being able to look up a kanji based on the keyword at jisho.org if for some reason you feel inclined to do so (e.g. you're reading manga and don't know the reading, the dictionary won't recognize the kanji you draw, you don't want to look it up by radical, etc). It's not that hard to just type the keyword or something similar. Chances are the kanji you're looking for will appear on the right or be displayed in one of the words below.
For instance, I've reached the 4k mark with Core 6k fairly recently. Lately, I feel several of the new words I learn are at the very least somewhat related to the keywords I learned, if not fairly predictable. In my reviews, there's always a word here and there that makes me feel like I don't really know it... but because I'm used to those kanji readings, I can safely get the pronunciation right, and by looking at the kanji I get a pretty good idea of what the word means. If anything, it's actually annoying when a new word is one of the few cases where my knowledge of kanji doesn't help understand the meaning at all. It's definitely noticeable.
Even if a kanji has more than one meaning which you may not have learned with RTK, it's not like you have to learn all of them right away anyway. I do fail to remember keywords all the time, but it's not just the keywords. Your stories can usually help you remember a little bit of the nuance. Sometimes, you can't remember either, but have a good idea what that kanji means anyway. Another thing that I do sometimes is look up the meaning of the kanji and read my story again briefly (if I feel the need and can't remember) depending on the word I'm learning.
There's also the advantage of being able to look up a kanji based on the keyword at jisho.org if for some reason you feel inclined to do so (e.g. you're reading manga and don't know the reading, the dictionary won't recognize the kanji you draw, you don't want to look it up by radical, etc). It's not that hard to just type the keyword or something similar. Chances are the kanji you're looking for will appear on the right or be displayed in one of the words below.