From considering that kind of thing, there's no level where you can learn it, then stop learning and retain it forever after. If you do stop, your memory and skill with it will fade ("I used to be able to do that!").
I imagine its because its has no use in my everyday life
Not at all; lots of hobbies and interests have no everyday use but are still attention grabbing, interesting, captivating, etc. People who spend time doing crosswords probably don't do them because crossword puzzles have use in their everyday life. Most people who play instruments don't earn money or give everyday performances. Most people who read fiction probably don't think it has use.
Maybe you're not lazy, and you don't really want to learn Esperanto, don't find it interesting, but have become trapped in a pattern of thought of a vague feeling that you "should" for one reason or another?; fear of missing out, or to be a good and respectable person in some way, or because it would make you more interesting, or give you an excuse to avoid a more difficult language, or uphold something you told someone you would do that one time, or any number of other not-too-convincing-when-you-look-closely reasons?
'Study' is what we have to do for things we don't care about. We have to forcibly prioritise them because otherwise lack of interest means we ignore them. Things we really take interest in, we do them. They don't need artificial studying and they don't need prioritizing, they may need other things pushed aside to make time, because they are already a priority ("I want to see what happens in this book, better make time for it").