Olive oil is one of the four basic ingredients. (In addition to tomatoes, garlic, and salt.)
In terms of taking the edge off of tomato sauce, shredded carrots works pretty well. I don't use sugar in any of my cooking, and no one has noticed.
If you think that's not true, simply take a sugar-low bread (check the food label, don't just go for organic/whole-grain, those usually have more sugar) and taste it for a while in your mouth. You'll notice it starts to become sweeter in your mouth.
As long as you stick to proper bread without the crazy added sugar, and preferably whole grain (actual whole grain, not just marketing "whole grain"), it's not an issue. Unless you try to subsist on literally only bread, of course.
The end result is that most people find the taste of non-pumped chicken unappealing, because they're simply used to the faked-up salt/sugar chicken.
Sugar content in pasta sauces is almost random. Varies from 3 to 10 grams per serving at least. It seems to vary more than almost any other premade item I buy.
And yet, even though I still eat junk too often, and like some treacle, I would not sort sauces based on sugar content.
I can't tell if there's no correlation or if it is literally reversed for my taste buds, but often the high sugar ones are the worst to me.
Just a theory, but maybe the sugar enhances some flavors, like garlic, but masks others, like basil, rather than drawing them all out equally?
I'm not sure how well sugar's complex affect on taste is understood by food scientists, let alone smaller or newer food brands. (What do the generic brands have, a couple chefs and a couple rounds of taste tests? No idea.)
Maybe there are too many possible combinations of ingredients and market segments for producers to all agree on the proper role of sugar, and maybe they're mostly guessing.
If that's true, then we could all probably stand much less added sugar than we/they realize.
There was some lab-rat study super long ago where they got mice/rats addicted to sugar and cocaine, then let them pick between the two - and they chose the sugar every single time.