I agree completely. I will focus of Japanese because it’s the language I have experience with.

With a good order (RTK), optimal reviews (SRS) and putting 30 minutes a day it is possible to learn keyword to Kanji writing in a couple of months to one year. Make it two if you are a busy person. After that you need 10 minutes to maintain the knowledge per day. (I’m assuming 2200 Kanji).

People that did that successfully will recommend it to be done as early as possible as they know the boost in learning it provides.

I think it’s a trap, because it’s possible to get to a very useful level in the language while ignoring Kanji, and most people will be perfectly happy staying there. At that point you will have a much better idea if you really need to go all the way.