It's an often-repeated time saving tip to marinate meat: toss the meat in a sealed bag and pour in a bottle of salad dressing for a cheap and easy marinade. Unfortunately, the high acidity in most bottled salad dressings do little to help the flavour of the meat and instead break down the protein bonds and turn it all mushy.
Make no mistake: a good marinade needs some acid like lemon or lime juice, or some vinegar, but most bottled salad dressings are way too acidic and are loaded with sweeteners, preservatives and other ingredients that you'd never put into a marinade if you had time to make it yourself. Plus, according to America's Test Kitchen, the end result is actually an oddly gelatinous consistency. They also note that long soaks in marinades, especially heavily acidic ones, actually don't impart much flavour to the meat, contrary to popular belief. Instead, just make your own marinade from fresh ingredients to taste, or make your own and store it in a squeeze bottle or jar in the fridge until you need it.
3 Things You Thought Were True About Marinating [America's Test Kitchen]