>>7763281You asked nicely so I'll explain in broad terms for a few general scenarios.
Baking sugary cakes or breads it actually generally doesn't matter that much. Cakes cook to an internal temperature of about 290F most of the time and as long as they reach that they're good. Baking powder reacts with heat but if it takes too long to heat up the cake will bubble out and deflate from a combination of too much bubble and not enough structural integrity. The main reason to preheat your oven for sugary things is consistency, ovens all heat up at different rates with different models in different weather. Baking a cake in a cold start oven that will climb to 350 degrees in 5 minutes is probably ok, but baking in one that takes 20 minutes to climb ill result in your cake deflating.
For yeasted breads and heavily gluten dependent baking it's all about forming crust properly. Same general idea as the cakes, properly proofed bread will continue to rise in an oven, but it shouldn't rise a ton or else the gluten bubbles pop and again you have deflated bread. Yeasted breads are also way less sensitive to overly high temperatures than overly low temperatures, so preheating is just always a good idea cause it's way worse for your oven to be not hot enough than to be a bit too hot.
For meat it's really fucking specific. Meat generally doesn't dry out due to time or holes from a thermometer, unless you're making jerky the only reason meat dries out and gets bad is from overly high temps. The fibers contract and squeeze out moisture, thus dry and stringy. Certain meats and cooking methods bypass this such as braising and pressure cooking, both of which completely destroy the fibers and connective tissue and leave the meat tender. But braising requires many hours, and pressure cooking gets way hotter than an oven can. Assuming you want to cook a chicken in the oven, you can theoretically start cold and not preheat, monitor the temperature super close, and just blast the bird with heat in the last few minutes for a good skin. But unless your oven is extremely powerful and you have a good spice goop on that chicken already you'll probably just end up overcooking the rest. This slow start to an exact internal temperature is the theory behind why sous vide works so well, but meat browns and cooks at dramatically different temps, so the process is always two step. Ideally you'd cold star the chicken, cook to an exact internal temp, let it cool off on the outside, then blast it with a torch to crisp the skin. I've done it before and it works but it's fucking stupid inefficient. The thermoworks blog has a great piece about all this.
https://blog.thermoworks.com/beef/coming-heat-effects-muscle-fibers-meat/The last and most fucked thing that you can do in an oven is the super high heat stuff like pizza and broiling fish. Even the best ovens don't have flame broilers powerful enough to make a good pizza on their own, thus you use a pizza stone with a lot of thermal mass and heat it up really hot to make a pizza. That 100% requires preheating because ideally you shouldn't be cooking a pizza for more than 90 seconds, and the pizza stone requires a good half an hour or more to get hot enough. Again, ideally you can make your own pizza oven with bricks and stone outdoors and do it wood fired, easily gets twice as hot as your oven, but if you don't wanna do that preheating is a non negotiable technique and even with a purpose built brick oven you need to preheat. Cooking a pizza too long at too low a temperature just makes it gummy. The dough is high liquid content and very thin so it needs to be cooked fast or else it becomes cardboardy. You could theoretically do this in a giant cast iron pan on the stove and have a very similar result in terms of crust but the toppings wouldn't work well without top heat.
