How do you know if image issues are due to you, the photographer or the camera itself? (Specifically about noisy images)

Hear me out. I'd say I'm an advanced beginner photographer. I understand the overall concepts and principles like the exposure triangle, white balance, don't shoot high ISO to avoid grain/noise, etc.I mostly shoot in manual mode. Ive been practicing lately, a lot outdoors during golden hour. Mostly portraits.So a little context here - I've taken photog class before in the past but due to some financial hardship I sold my camera. This was years ago, so I'm not very well versed in the technical hardware/tech part of cameras today. Recently I decided to get back into it, and just to start out I bought a Canon EOS M50 Mark ii (purely because i got a crazy good deal on it). I think this is relevant to show I may be missing something important about the camera build itself.I've been using it with an adapter and a 50 prime lens. I'm noticing during edit of my RAWs that when I zoom in most of the background is REALLY noisy. It bothers me so much.But I can't figure out if this is due to my photography skills (or maybe lack thereof) or the camera itself. I'm not shooting at any crazy settings. The subject looks pretty good, maybe soooooome noise but not as bad as the shadows in the background.I just checked one of the images and it has the following settings: f/3.5, SS 1/200, ISO-100Am I missing anything important here before I go blame the camera? 🙃 via /r/photography https://ift.tt/3flEfrX