Is weight loss really just calories in vs calories out??

Fundamentally, yes, all you need to do to lose weight is ensure that your caloric intake is less than your output. The nuance of that arises in that most of your output (unless you're extremely active) comes from your basal metabolic rate, and there are a ton of factors that can increase or decrease that to affect the "calories out" figure in ways that can be unexpected and/or hard to predict. To keep that as high as possible, you generally want to be at least somewhat active (regular physical activity will increase your BMR beyond the active calories you consume), make sure you're getting a reasonably balanced diet that includes all the vitamins and minerals you need, and not restrict by more than about 10% of your energy needs.

Of course, the other issue is that counting calories is harder than a lot of people realize (especially when most figures you see are very rough estimates, often with margins of error greater than the margins by which you should be restricting) and can very quickly turn into a disordered obsession if you try to take it too seriously. Instead, try to get more active, make sure you shore up any nutritional deficiencies you have, and slow down your eating so you can get better at stopping when you're satisfied. Once your caloric demands stabilize, then you can start eating slightly smaller portions of everything.