Tough question. I may go off on a tangent here, but theres a fine line you tread here. You are going to piss people off by making change, or by not making change. The idea is to make mostly the right changes in terms of balancing what the customer wants, what the majority or your clients or the area wants, and what you want, and of course, giving them value for money along the way.
At the end of the day, you really need to cook food that fits into the area you are cooking for. A town or part of the city which is uncultured is not going to appreciate fine dining to make a very obvious example. SO if you are cooking food that fits the area then it's a great start.
We as chefs know probably better than the customer what is good and what isn't. What i mean by that is we do this job for a living, our livelihoods depend on making really good tasting/looking food. Having said that, everyones palate is differant, so straight off the bat it is impossible to please the vast majority of customers. So when a customer complains or approaches me with something about the menu, no matter what i will listen. But that does not mean i willl immediately change that menu item. If they thought it was overseasoned and you thought it was correct then it more than likely is. However, if 4-5 tables have complained that it's overseasoned in the same week, and you think it's alright, perhaps you have a chef palate and you need to rain it back a little.
Trying to break this down into two examples which i feel restuarants fall into that are unseccesful.
Theres a balance you find here, if you do everything the customer wants, then they expect it next time(which leads to horrible floor issues among other things, but not getting into that). So you really need to do that for each table to be fair. So now you need to change the dishes so much in service it becomes hard to get the food out, suiddenly the customers now have something else to complain about - inconsistency and slow food.
If you don't listen at all. Think your all that, and you think you are the god of cookery, every dish is perfect and you think anyone who complains is an idiot. Then you may not be cooking for that laocation, your numbers will dwindle, people will get pissed off and your menu is likely to not evolve with the times at all.
In regards to doneness of steaks. You will always get complaints. It's usually one of three main problems.
Floor- we need to train(or FOH manager) staff to actually ask these things when taking orders. I always ask if there are any allergies we need to be aware off, and when ordering a protein which isn't obvious then ask how they would like it cooked.
Chef- Cooking steaks classically isn't easy, especially in a busy restaurant. You have to allow for a lot of things to get them just right, the main one being residual heat and resting. Now i can't comment on your restaurants, but i've seen a lot where the chef thinks they have done a great job, but it falls below par a lot more often than it should. To combat this procedures and training need to be put into place in regards to hot you cook it/rest it/ serve it. Sous vide cooking has taken the guess work out of a lot of these things, the main one being you no longer need to allow for resting times. but it comes with other challenges like getting the protein hot enough for guests and getting a nice char on it. If you are the head chef, you should be constantly checking these things to make sure they are going out correctly. Beleive me, you won't get complaints if the steak is cooked and seasoned well. usually comments like " oh i'd prefer it to be a little more cooked or whatever)
Last one being menu structure. If you do get a lot of poeple wanting well dowe steaks, put braised beef cheeks on the menu as well as steak, simple but very effective way of making sure they enjoy their meal (again, FOH need to know how to push customers into ordering this as well done).
hope these ramblings help