I also had experienced it many months ago with my Note 4, and it had also started capturing photos with low quality. It had lost image quality, images were now a little yellowish and a bit blur. Images were not as sharp and vibrant as it used to be when mobile was new. So, I also had started believing in the idea that Samsung mobile cameras aren't good for mobile photography as they lose image quality slowly.
Later, one fine day, I just had a glance on the lens of my mobile camera, and OMG, it had dust, I gently tried to clean the lens but it didn't work, because it the dust was inside the lens, I wonder how the dust particles managed to went through inside the camera lens when the mobile body is boxed so well.
(a demonstration of dust on the lens of mobile camera)
Anyhow, having no idea about how to remove dust particles inside mobile camera lens, I went to a mobile repair shop and told him the issue. I had many thoughts in mind at that time, thinking he'd might charge a hefty sum as he might have to replace the whole lens system, but to my surprise, all he did was that he removed the battery, took a sharp tool like knife, removed the camera lens and cleaned the camera lens and sensor with a tissue-like piece of cloth, and guess what, within just 2 minutes my phone camera was working as incredible as it used to work when my mobile was brand new. Later, after a few months, I did it my self and cleaned the inside of mobile camera lens and sensor.
How to remove dust particles inside mobile camera lensIf you are little proactive person who do not hesitate trying and learning new things, do it yourself, but make sure you clean the sensor of mobile camera extremely gently and carefully. But if it seems a a difficult job to you, go to a near-by mobile repair shop and ask the guy to do it.
(a demonstration of removing lens of mobile camera)
I said all this in Samsung case, but other brands are not an exception, their mobile cameras can catch dust as well, so you can try this handy DIY on other mobile brands too.