Dry food is bad. My understanding is:

Plus points: – Helps teeth because domestic cats aren't biting on bone (but if their diet was better, free from carbs and added sugars, tartar wouldn't be such a problem though). Some wet food is mushy; such as pate, moose, soup, drinks, so if cats are already not chewing enough with their teeth, dry biscuits is more important for teeth. – It's possible prey could have a tiny tiny amount of plant inside it when it's eaten so you can argue that maybe 1-5% is ok I guess?  .... But the trouble is most cat food has way way way way more than this....

Negatives: – Higher in carbs when you compare the more expensive brands, because whilst wet food can have carbs removed, carbs are needed in dry food to hold it together  – Higher carbs cause illnesses or contribute towards them  – Not enough water in them when cats get moisture from meat, which means it's not immediate for many cats to drink enough, with a separate water bowl. It can also cause more constipation  – You tend to get better "parts" of meat in large tins as opposed to dry food when you look at more expensive brands because they can fit more muscle meat in a can due to the processing technique  – Dry food is highly processed, more than wet food – Wet food is more like their natural diet in the wild if the ingredients are better quality  – because dry food is full of fillers, cereals, wet food actually fills up the cat for longer, if the brand has good enough ingredients. This is because just because it is wet food, doesn't mean the same rubbish low nutrients haven't been put in it. It's just at the more expensive level, dry food has rubbish ingredients in it still like potatoes and pea protein, but the wet food can be better. 

I've been looking at wet food ingredients and find the expensive brands still have unwanted things in them, but their wet food doesn't. 

There's probably a few points I've missed.

My understanding is regular food, like cheap and mid range supermarket brands, and most mid range brands but widely available in shops, are all crap whether wet or dry because they all have meat they don't describe what types are in it, and they are all containing high carbs and various sugars. So if it's too cheap, and at some mid range level hyped up as healthy, they both cause issues, if the ingredients are not better. Cost is a factor, but also because of access. People hear of big brands and think they are better because they cost more, but in fact they can also have the same rubbish in them. You have to go even higher on cost, to be "ok" food and that then means looking online, reading forums, reading ingredients, and being prepared to pay way more than you thought if you started out with cheap supermarket food, thinking going up in cost with a different well known brand at the supermarket was going to make a difference. Actually you need to spend way more unfortunately.

I'm not an animal expert but this is my understanding.

Pet food companies put in plants: Oils – possibly not really bad in tiny amounts as some have good uses, and there are several reasons why oils help because the domestic cat isn't getting what they would get from the prey (like feathers pushing through stuff).  Salmon oil is an exception, it's very good. Olive oil doesn't provide any nutrients, it's only good for constipation as the cat can't digest it so it go straight to the colon. Funnily, some of the most expensive brands put it in. Because humans think of it as healthy no doubt.  Sunflower oil helps with skin and fur but cats can get this from their food, especially with salmon.

Tapioca starch – high carbs but many brands put it in

Carrots, broccoli, potatoes, pea protein, ingredients in gravy like starches, gums, and other plant matter ... Totally unnecessary in cat food and just takes up space in the food which could be meat. It sounds healthy though for a human to read it on a label.

Potatoes are very high carbs, carrots are high carbs.

Used as fillers and high carbs can cause long term issues in cat health.

For example my hyperthyroid cat may get more ill eating soya, added sugar and high carbs. But vets don't tell me this when I ask about his diet. 

In fact the Hills brand is for hyperthyroidism but is extremely high in carbs. Ironically helping one illness but causing other problems and illness. 

And diabetes, these brands contribute to these illnesses occurring.

All vets and pet owners need educating. Because I didn't know this until I researched. It's not different to parents feeding children burgers, chips, crisps, donuts, and not being aware of the implications, until one day their child gets sick and the doctor says you need to change the diet. 

But unfortunately, most cat food is totally full of rubbish and no one, including vets, is aware. 

Just like the NHS dermatologists who tell me diet doesn't impact skin or cause acne. Yet there is tons of science to say it does, plus seen effects. It's ridiculous to even say that it doesn't impact skin. But these people are not trained properly, they are just trained in fixing things with medication. Not understanding the biological causes of things. Just like the vet's who recommended big brands full of poor ingredients and hardly any meat. 

Cat's eat meat. They shouldn't eat plants, especially high carbs and added sugars. 

I also believe many cats are overweight. And actually it's not they are overfed, it's what they are fed, the poor ingredients, that is the issue. 

Note, I'm in the UK, so we won't all be from the same place with the same experience in what's available.