One of Bruce Lee's often quoted sayings is "Absorb what is useful, reject what is useless, and add what is specifically your own." I also advocate absorbing what is useful; that which is useful in most situations that are likely to occur, not what is useful in a specific situation that may never occur. Most people will live their entire lives and never have to defend themselves in any type of situation. If a self-defense situation does by chance occur, it will probably be the last time it or any other occurs. So, does it make sense for students to spend their training time learning techniques that are only good for specific situations that may never occur, or should they be perfecting a few techniques that may be adapted for use in many different situations that may occur. Unless you have a desire or particular need to learn as many techniques as you may find, then you should reject techniques that, although not useless, are not useful for you in your life. There is nothing wrong with trying a new technique. It may prove to be useful, or it may be useless as is but you may be able to add something to it to make useful for you.
Instead of seeking to learn as many techniques as you can, a better way to approach learning is to seek to learn all you can about a few techniques that work best for you from as many different instructors as possible. Many instructors may tell you the same thing, which reinforces what you already know, but sometimes one or more may tell you something you do not know that will help you perform a technique more effectively or efficiently.
Absorbing what is useful and rejecting what is useless is a noble goal, but it is similar to the goal of only absorbing the truth and rejecting lies. The problem with both goals is: how do you determine what is useful or useless, or what is true or a lie? Is a technique useless or a fighting theory false because it does not fit into your style? Or, is a technique useful to you just because it is used by your style. Sometimes it is difficult to sort the wheat from the chaff.