Well the trouble with wanting to find/set a single, simple definition of what is 'healthy' is that people are all different both in terms of their health (as you yourself say, you have kidney stones so some generally 'healthy' foods are not at all healthy for you) and also their lifestyle and preferences, e.g. some people are vegetarians, some people need to have meals they can prepare quickly and easily, some enjoy spending hours in the kitchen. Basically all foods can be 'healthy' for some people some of the time (even very sugary/fatty processed foods could be exactly the right thing to eat if you are someone that is very under-weight and urgently needs easy to digest calories for instance). People can be evangelical about food but personally I am always really suspicious of anyone saying their diet is the one and only true/healthy/effective way to eat, especially if you are being asked to pay money for it 
Controversial statement (on MN anyway) incoming, but I think purely in health terms (not weight loss per se), if you are after general, clear guidance, easy to follow and practical to implement for 'ordinary' people, the NHS EatWell stuff is still the best - loads of detail about it online and there are parts of it that some disagree with, but the majority of dietitians and dietary scientists agree that a Mediterranean style diet (which the NHS EatWell broadly is but adjusted for mainstream British tastes/preferences e.g. not too much fish as many people dislike it) is overall the best, including lots of fruit and vegetables, legumes and pulses, some wholemeal carbs, a moderate amount of lean protein and unsaturated fats, very small amounts of red meat, and avoid or minimise 'junk' - sweet things, alcohol, crisps etc. Increasingly there's a school of thought that says you should minimise ultra-processed foods as well. Following the EatWell or another Mediterranean-style diet guidance alone is unlikely to make you lose weight fast or at all (unless you are very obese and/or were eating huge amounts of junk) but should improve your general health.
If you do want to prioritize weight loss specifically, in general you do need to create a calorie deficit, which is a bit different from just 'general' healthy eating. Some people do this simply through vigorous portion control and calorie counting/tracking, so if simplicity is what you are after that may be the best way. But for many people, they find calorie counting quite restrictive and the most effective/easy way to lose weight is by some combination of reducing their carb intake (in particular white processed carbs like pasta and bread) and/or some intermittent fasting (where you have an extended period per day of not eating and/or eat a reduced amount on some days of the week). I know the proliferation of information on here is confusing but I would take some time to browse the threads on here - the low carb bootcamp threads, the 5:2 and 16:8 threads, the thread called 'why we eat (too much) - these are long and quick moving threads but the opening posts nearly always have a nice quick easy to read summary of what the diet is all about, and people often post examples of their daily menus, so I would browse all that and have a think about what would suit you best. Then pick something and really give it a good go and stick at it for a long period of time, a healthy/sustainable diet is not going to cause weight to crash off you so you will need patience, the main reason most 'diets' fail is either they are too restrictive/impractical so people give up very quickly or they work in the weight loss phase but people then return to old habits once they've lost the weight hence 'yo-yo-ing', so it's important to find something that works for you even if you only lose 0.5lb a week or something?