There is no question about it, tracking your calorie input is a bit of a pain in the ass and some people consider it obsessive (usually people who find it easy to maintain their weight).
That being said, tracking your calories is one of the only things you can track when it comes to weight management.
It is a great tool for helping you consume the right amount of calories for you and your goals
It takes away a lot of the guesswork
It can highlight foods and drinks that are high in calories and can help with correct portion sizes
It doesn't need to be done forever but is hugely useful in teaching you how much you should be eating.
If you're looking to lose weight, 9 times out of 10 you've gained weight by eating too much or paying too little attention to what you consume. Tracking your calories can help you be more mindful and help to get you in a calorie deficit to lose weight.
Is it completely accurate?
No. You'll use a bit of guesswork, food labels aren't totally accurate, some foods are absorbed differently in the body etc. However, it's good enough.