The reason why restaurant spaghetti tastes better is because chefs and cooks in restaurants use precise techniques like finishing the spaghetti noodles directly in the pan as well as emulsifying with starchy pasta water and even generously layering fats and seasonings.
The key steps that restaurants use to make spaghetti taste so great includes, finishing in sauce, the starchy water, generous salting and layering fat and fresh ingredients.
Instead of just simply pouring sauce over plain noodles, chefs and cooks in restaurants pull the spaghetti from the boiling water a minute early and then they transfer the spaghetti straight into a skillet of sauce while it's still hot.
The pasta when placed in the sauce that is hot finishes cooking in the sauce and absorbs the flavors of the sauce and creates a unified spaghetti or pasta dish.
Chefs and cooks in restaurants also save a cup of the salty, starchy boiling water and then add it to the sauce.
This salty, starchy boiling water acts as a binder and creates a velvety, cohesive coating, instead of having the sauce slide off the spaghetti.
And water in restaurants for spaghetti and other pasta is also heavily salted, which is often described as being salted so much that it tastes like the sea, which flavors the spaghetti and pasta from the inside out.
Chefs and cooks in restaurants also added fats like quality olive oil or butter at multiple stages, when making spaghetti and pasta to round out flavors and get a luxurious mouthfeel.
The chefs and cooks in restaurants also prioritize using fresh ingredients in their spaghetti and pasta dishes, like fresh basil, instead of using dried, stale pantry seasonings.
You can also easily replicate these steps at home and make restaurant quality and restaurant tasting spaghetti at home.
It can also take some practice to get the spaghetti to taste like restaurant spaghetti at home, but it can be easily done.