It depends on the dish you are making. Tomato based, you can use oregano or basil. Chicken tarragon. Rosemary for beef, pork. And it is ok to leave it out from the recipe.
For shrimp salad, I'd use basil instead.
I've used bay leaves or just left it out of the recipe.
I agree about the basil.
But also depends what type of shrimp salad - if it's made with a creamy dressing, I love fresh snipped chives and/or dill with shrimp salad. With a dressing made of olive oil, vinegar or lemon, etc. fresh chervil might be nice with the shrimp. It's mild and fresh (also I think one of those underused herbs, like marjoram.)
I agree with dill for shrimp...but thyme is a milder herb than basil..great for tomato or Italian dishes, otherwise,.I'd use oregano in other options or just omit it.