There are few places completely off the tourist radar in Switzerland, but I've definitely noticed that certain nationalities gravitate towards certain destinations. Obviously a lot of tourists also have limited time, so they understandably tend to hit the "top 10" sights and skip smaller destinations. If you are a repeat visitor or have more time, there are many other options. If you're a hiker or walker, there are literally hundreds of choices!
Nature: Berner Oberland is great and rightly prioritized by many American visitors because of its convenience and beauty, but when I want to go to the mountains in the summer, I usually avoid the whole region (unless I have visitors from the US!). If you want to enjoy spectacular mountain scenery without massive crowds, especially in early summer up until mid-July before European summer vacation starts, head somewhere like Arosa or the Engadin in Graubünden. These are famous as winter sport regions, but offer great hiking and scenery in summer without the BO crowds. Unterengadin in particular is a great place to visit off the beaten path - check out the area around Scuol-Tarasp and Guarda. In the Oberengadin, skip St Moritz and go to Sils-Maria/Celerina/Pontresina instead. Not exactly undiscovered, but beautiful places with fewer tourists, especially earlier in the summer. Grächen and the Saastal near Zermatt are also great outdoor destinations.
Closer to Luzern, I am always amazed at how few Americans visit nearby Engelberg/Brünni, Stoos, Klewenalp or Melchsee-Frutt, especially for hiking. I get that many people let the Swiss Travel Pass dictate their itinerary due to cost concerns, but that leads everyone to visit the same few mountains - so if you're staying in Luzern and have a Tell Pass, for example, be adventurous and try a different mountain - wonderful scenery with fewer crowds than Rigi or Pilatus guaranteed!
Other areas: Maggia Valley region in Ticino; Fribourg and the Schwarzsee; Bielersee wine villages and Neuchâtel; and I have to put in a good word to my home canton Aargau (Hallwyl and Lenzburg castles, Habsburg castle ruin, Augusta Raurica and other roman ruins, Baden, Aarau), can also make for good day trips from Zurich/Basel/Luzern.