Humble can of plain chopped tomatoes is the one thing that keeps my diet interesting and relatively nutritious. It's the base of my little cooking framework that allows my lazy ass to eat warm meals on a quasi regular basis.
The only fresh produce you need are onions, but you can buy a lot of them at once and they won't spoil too quickly. Just brown chopped onions on olive or vegetable oil, pour a can of tomatoes, add salt, pepper and some italian style dried herbs and you have the most basic pasta sauce that took maybe 10 or 15 minutes to make and you have sth for dinner for the next 2-4 days depending on the size of the can. But its true strength comes from its versatility. You can add any random thing you have in your pantry and it still tastes good. You have broccoli in your freezer? Just add it and wait until its soft. Same with anything else frozen. Everything canned goes as well: green peas, corn, string beans, chickpeas, beans... Want something heavier? Add fried minced pork or beef. You can also poach eggs in that sauce. Want to keep it vegan? Fried or baked tofu. Frozen or dried mushrooms? Of course! If you are not sure about some ingredient just add it anyway. It will still taste like a tomato sauce. It only tastes better with fresh produce but you can keep it 100% canned + that inital onion and it's still a solid option that keeps your morale high and your body nourished enough to avoid unnecessary long term problems. Just keep it simple and it's foolproof.
As far as safety of canned food is concerned, I haven't seen any hard evidence against it. It's not a new thing. If it was fundamentally harmful we would already know about it. Just don't exclusively eat readymade canned meals or WW1 western front rations. Also mandatory ~~reddit~~ lemmy style sorry for bad english.
In general avoiding situations when you only rely on your willpower gives much better results than fighting yourself. When I think I should loose weight I only buy boring ingredients that require preparation to be tempting in any way. If I get strong cravings I just eat some random vegetable and try to better plan mealtimes next day. It's much harder when living with uncooperative partner or parents that like always having snacks in their kitchen. We're literally built to eat food whenever it's available.