Exercise is far from pointless.
Firstly it's irrelevant how many calories you burn. What's relevant is how many calories you eat.
Eat the same as you burn, maintain weight, eat less than you burn, loose weight, eat more than you gain weight. You are doing the first.
So it doesn't matter if it's 200 or 700. You're eating those calories back.
If you don't do this, you will loose weight.
Secondly exercise tones you up. Changes your body definition. So instead of a body with no muscle definition and kinda flabby you look much much better both in and out of your clothes.
However if you think exercise can help you loose weight, whilst you just eat more to offset the exercise, no that doesn't work. You need a calorie deficit. You need to do it in conjunction with diet.
But if you want the toned arms, the flat stomach, the pert back side, the toned thighs, as well as the weight loss, then this is where exercise comes in.
And that's before any of the health benefits, inc mental and physical.
Don't give it up, but if you want to loose weight with it, then yes you need to manage your food intake st the same time.