Chemicals ≠ chemicals. Some are safe, some are not safe. Some you can have a lot of, some need moderation. Some are artificial, some are not. Those people just can't not think in black and white.

The bigger issue that a lot of the worst parts of food aren't really modern, they're just more accessible in modern foods. Like excessive amounts of salt, sugars, and fat, all of which are fine and necessary in certain quantities but which get used in a very imbalanced way. These preserve food and when used correctly improve its flavor, but in a lot of modern slop get overused in a form that's specifically engineered to avoid satiation and keep people buying and consuming more well above the level of what they want or need.

There are also additives like dyes and stabilizers that might not be great for people to eat, but which still pale in comparison to the carcinogenic (and other, also harmful) effects of just like chugging bottles of syrup for hydration or relying on heavily salted instant food.

And that's before you even get to issues like heavy metal contamination and whatnot, that aren't intentionally added but which show up anyways.

Also, a lot of really effective food preservation today don't even require chemicals inside the food.

Exactly, like there's pasteurization and irradiation and sterile airtight packaging which can replace or supplement what are basically just more advanced versions of traditional preservation methods like giving food a PH that bacteria and fungi can't tolerate, using salts, sugars, and fat to make it too desiccating to spoil easily, etc.