I have canned for decades... Here is my take...
If you have access to bulk foods you get for little cost, it is worthwhile. My inlaws ran a commercial apple operation. I got apples for free. I made tons of apple sauce. Definitely worthwhile. But f you buy bushels of apples to make applesauce, its cheaper to buy prepared. Got a big garden? Canning is the way to go. It saves freezer space for other stuff...
If you buy in bulk and want to preserve, its great. Hamburger is on sale at $1.99/lb instead of the usual $5.99? Buy 20 lbs and can up sauces and chili.
If you like quality food, it's fantastic. There are nights I am exhausted from work. I'm hungry and want a good home cooked meal, but too tired to really cook. I open a can of my home made spaghetti sauce or chili and its a fast, low effort meal.
It does take work, effort, and some cost. You need to buy jars and lids. Watch for end of season sales on lids, and stock them deep.
Quick run down: Water bath canning is high acid foods only. Very easy to do with minimal equipment and cost, but its limited to jams, jellies, pickles, tomatoes and little else. While all you really need are jars and a large pot for equipment, each jar of jam or pickles or tomatoes either requires a fair bit of ingredient inputs (Vinegar, sugar, fruit, depending on what you are making) or a ton of labor (tomatoes are time intensive). Pressure canning is the only way to reliably and safely can meat and low acid foods. You need a pressure canner, which can be expensive. However, inputs are often less intensive cost and labor wise. At times, I have simply stuffed chunks of meat in a jar, filled with water, slapped a lid on, and pressure canned. No need for vinegar or other acids....
a pressure canning pot can be used for pressure canning and for water bath canning. A bit water bath canner can only be used for water bath canning...
A tip: Go to Walmart or look online. Buy Ball's Book of Canning and Preserving. Well worth the $10 or whatever it costs...
Shelf life.... I have jam and jelly that is five or six years old. It is fine and safe. Over time the jams become darker, and loose some flavor. Instead of a 'fresh' this-years-crop strawberry jam that is bright red and really 'berry', it slowly becomes darker, deeper red and while still strawberry flavored, becomes sweet with less bursting berry flavor. Green beans are great for several years with no loss in quality. As long as the lids are still sealed tightly to the jar, the food inside is "good" even if there is a slight change in color or taste. And a tight lid is entirely and purely the result of your careful canning technique. Use a clean jar, with a good clean lip/rim, use the proper dome lids, can per the recipe, let cans set after canning and DO NOT FUSS WITH THE BANDS/LIDS. let them cool completely and absolutely before touching the bands. check for good seals.
If Some high acid foods are a bit more problematic: The acids in the foods can attack the underside of the lid and start eating at it. Over time, the lid can corrode. It doesn't happen often, but it's possible. This isn't just home canning: Set a tin can of pineapple on your shelf for three years, and at some point it will fail when the acid eats through the damned can...