Putting any seasoning on a meal you are served without tasting it first.
If it is not to your liking, then add the ketchup, steak sauce, salt, whatever, but at least try it first. 1) Out of respect for those who prepared it. 2) You might find that you enjoy it as it is.
Now if you prepared it, by all means, do whatever you want to it.
Good questions. In my opinion, I think if it is fast food or delivery, do whatever you wish. Similarly, if it is a food you’ve had at a place before and remember it needed more of XYZ spice/sauce, it is fair to add it prior to eating.
For new experiences, especially with company, at a nice restaurant, or at someone’s home, definitely taste first.
But in the end, as a fellow poster stated, life is too short, enjoy whatever makes you happy.