Not sure how authentic this is but try: Fry off finely chopped onion, garlic, celery and carrots (You can try different quantities, but usually 1 of each) Add oregano (or any herbs really) and I usually add dried chillis and a couple of bay leaves. Add tinned tomatoes or passata and probably 1-2 cups of water and then just leave it for an hour or two. You can, at any time add wine or some worcester sauce, but this will make it quite heavy. The sauce is ready when the 'raw' tomoato taste is gone. I usually then blitz it with a hand blender, which I think improves the taste, but some people prefer it chunky. It's all trial and error, but you can't really go wrong with this!
It might well be the tomatoes. My wife's Italian colleague swore she was never able to recreate her proper pasta sauce with the toms available in Switzerland, even if she folowed the recipe absolutely correctly.
And don't forget to add a pinch of sugar as well just to enhance the flavour of the tomatoes (from my Italian nonna). As Paddy's wife she never used fresh tomatoes.
Often people add some sugar to reduce the acid of the tomatoes and then add some vinegar to counter the sweetness and create a 'tangy' flavour. I'm not a fan and in Italy they reduce the acid in the tomatoes with carrotts and celery, which I much prefer. I'm not sure how true this is, but I have heard that in Italy they never mix onions and garlic in sauces. They use one or the other.
Definitely use passata rather than tinned tomatoes - I think it gives a richer sauce. The quality of the herbs are important as well. Mrs TH's parents came back from Greece with some dried oregano that was the best we have ever had. Just experiment with what is available.
I chuck a good load of wine in and let it simmer away for as long as possible. The longer it's on the heat the better it usually tastes, although I prefer a thicker sauce that will stick to the pasta. I would add a stock cube (I think the Knorr stock pots are available here?) to the meat as well, along with some tomato puree with the veggies.
Definitely trial and error, and the beauty of a sauce like this is that you can try almost anything. Maybe some halved Peppadew peppers to spice things up a bit?
Tangential tip.....tomato flavour is fully developed by the interaction between the flesh and the juice of the tomato - those two elements react with an enzyme to develop the flavour of tomato. This enzyme is destroyed at 4C and doesn't reactivate, so never keep your tomatoes in the fridge if you want it to taste of tomato. Taking them out of the fridge an hour before doesn't help
The sauce gets more acidic/tangy the longer you cook it, particularly if you leave uncovered. I've never heard of putting in vinegar. Tinned tomatoes, tomato paste, garlic, basil, a little oregano, and some red wine. Carrots will help pull the more acid taste out and leave the tang. We throw in a few slices and pull them out later. Yum! Now I am craving spaghetti!!