A “tourist” restaurant is a large restaurant with an industrial kitchen and often coach parking nearby. It is designed to serve tourist groups fast with a boring international set menu and, sometimes, a “tamed” local specialty added. That pretty much defines what you ate on the flight over, right? It is not bad, but certainly not memorable. On the positive side, you are not going to be surprised with odd exotic flavors and you will be in and out in no time, group tours do lunch or dinner in one hour flat! It is also likely to be inexpensive assuming the restaurant offers the same menu to walk-in tourists as they do to booked tours. The downside being that the meal can be pretty bad (but you will not get sick! Because tour operators generally do not care about quality or taste as long as no one gets sick), overly priced (the price shown on menu may be far higher than what groups actually pay … because it makes the group tourists think they are getting a fancy and expensive meal!) or you sit and wait, being ignored while they serve two groups of 50 tourists.
Having said that, some tourist restaurants are actually a good deal serving a fair meal quickly for a moderate price. Sometimes, they are unavoidable because of the location. For example, Jungfrau, Gornergrat (where you go to see the Matterhorn) and Zugspitze feature above average “tourist” restaurants all serving excellent meals, which is quite a feat as they are all higher on the Alps than aircraft cabin altitude (read why food taste bland up there on another post: "Airline food is looking good!").
Now for the truly “bad” tourist restaurants, the ones you have to watch out for. Typically they are too small to accommodate groups, so they don't have to care about repeat business or standards. They are always located on a high traffic tourist path with set menu posted outside in a zillion languages. That in itself does not automatically mark them as “out to get you”, what does, and what you cannot see on travel sites, is the complete lack of local patrons, especially the younger ones. Because even on the “tourist strip”, they are locals there … to work in the tourist shops and attractions. They eat and drink too! And the younger ones are typically more sensitive to meal prices. Of course, there are always a few pearls to be found, but considering your limited time frame you can't spend two hours searching for the perfect lunch spot.
Even with limited time and local knowledge, you can locate and identify fairly quickly a good and welcoming restaurant. First, you have to get off the strip and venture into the side streets where fewer tourists venture (but not empty of them!) and where rent is much cheaper (big impact on menu prices). If they have a menu posted outside in English, it is not a bad sign in this context, it shows that they do welcome tourists and if that menu looks interesting (no rubber chicken and meat in sauce) so much the better. Peeking through the window, you see some younger and obviously local patrons, then you have probably found the right place: it's not a tourist restaurant but a restaurant where tourists are welcome and likely to be treated well.