IIRC there's a nice hotel (Hyatt?) near Hoover Dam.

There also are some hotels up in the hills that seem far from the strip but most/all have casinos.

Within Vegas and even on/near the strip, there are a few hotels without casinos. IIRC Four Seasons (just beyond Mandalay Bay and attached, so that it's easy to get to the little train, etc.) is one example, plus there are a couple independent properties near Hard Rock (across the street) that are walkable to the strip. These would be three or four star places.

If you're trying to avoid the strip, how about downtown Las Vegas? It's not as upscale and seems a bit more oriented to the locals, but gambling is still very prominent here, even hard core.