Learning grammar without speaking is boring for many people, because their reason for learning English is to communicate. But learning only speaking without any grammar limits how advanced you can get, you will likely get to about lower intermediate level in speaking and much lower than that in writing. I often see students who learned mainly grammar and other students who only learned through speaking. Both have problems and are limited in their ability to express themselves.

Grammar is not simply a set of academic rules - it expresses meaning as much as words do. Simple example: when you change the order of the same words, it becomes a question. When you use the same verb in the Present Progressive as opposed to Simple, you can express the idea that the action is temporary, not permanent. That meaning is in addition to just the meaning of the verb itself. So without understanding grammatical differences, your speech and your understanding of other speakers will not be precise or sophisticated. And there are a lot of other ways that grammar makes a huge difference in meaning.

There are reasons why adults benefit from learning their second language grammar and cannot learn quite the same way as children learn their first language. Children do not become proficient in their first language until they are at least about 7, often more. They are immersed in their language every waking hour of their life from when they are still in their mother’s woumb . When they are born, they practice by trial and error, without any shyness to stop them, and get feedback from adults almost every waking hour. And their brain at that age is extremely plastic and most suitable for developing language.

We don't have all that time and other conditions when we are learning a second language as adults. So we need shortcuts, tricks and lots of motivation. This is where grammar rules come in very handy, as well as a good teacher who can combine the fun of speaking and communication - with helping you to easier understand and use the rules, the logic of the language system.

In short, there are different methods that work for different individuals. But the important principle is to learn to speak and to understand how grammar helps build the meaning.

In my point of view, I disagree with that.Knowing grammar doesn't mean that u will also speak properly.If u have information on a particular topic, it doesn't mean that u will be able to speak about it fluently. Mastering in conversation and speaking skills makes u ready for all the circumstances in life, where u have to prefer speaking than merely gaining bookish knowledge of grammar. For instance, a job interview is a perfect example for what I mentioned just now. The interviewer will not see your grammatical knowledge, what and how much do u know about it, wheather u are the best in it. But, how u speak, converse and interact with him, makes him think that u are absolutely perfect for the job. And let it be in any field! Let's take another example. Like if u read something about swimming, and try to swim, u will surely drown at the first attempt. But if u have only a little knowledge about it and u try practicing swimming, gradually u'll learn how to swim and that too, faster than the one with a lot of knowledge. Same goes with the case of language. If u don't know how to speak well, definitely your grammatical knowledge will be of NO use. Speaking is the base of language. And it is by speaking only, that we can communicate with each other and not by grammar.
So, in my opinion, practicing conversation skills is more important than studying grammar.