I am European and educated in Europe. I know Geneva well enough. My sister went to [a fancy private] school nearby. To North America IT IS NOT a premium market hence why you have very few routes. Within Europe it is primarily a leisure market due to its proximity to all the ski resorts. A rich leisure market but a leisure market nonetheless.
It is however a favored destination of the very rich but those folks don't typically fly commercial. Wealthy middle eastern businessmen love Geneva but to N.America it is a low cost market.
The A321LR will have a problem because the primary draw for GVA is ski traffic. I'm not sure how well the A321LR would fare, flying westbound TATL in the Winter loaded with ski equipment. It's probably a no-go.
It's high yielding because it's dominated by very short routes due to it's central location in Europe. Low Cost does not mean Low Yield. High Yields don't necessarily mean high profits. Yield is very skewed by flight length in favor of short segments.
You are actually not correct. In the long-haul segment, GVA is one of the few European airports that completely fills its F and C classes. More than 20% of travellers fly C-class or higher. Survey by Airplus shows that more than 50% of GVA long-haul travellers. To equate GVA airport yield to ski travel (~1.2 m travellers p.a. out of 17m) is not accurate given the economic wealth of the region: finance, trading & shipping (Cargill, Dreyfus, Mercuria, Trafigura, Vitol, etc.), luxury goods (Rolex, Richemont), multi global HQs (Nestle, etc.), EMEA HQ including many from the US like P&G, Du Pont, HP, Medtronic, etc., international organisations (UN, WTO, CERN, WHO, IOC, etc.).
FYI in July UA flights (EWR + IAD) were ~85% full, with similar loads across C, premium economy, and Y. In March, not a peak holiday month, ~90% in C, ~80% in premium economy and ~65% in Y (total ~75%). It is the same picture for LX. The problem for GVA is not filling the F / Y, because it is a premium market. It is filling the back of the plane, because it is a medium sized city (Geneva -Lausanne Area ~1.6m people across France and Switzerland) and lacks connection (not a hub).