There has been a debate some time ago about a more sensible market garden without the bridge at Arnhem, but the general opinion (which i share) is that the operation would have been useless WITHOUT Arnhem.
Without Arnhem the allies would have captured a few bits of land with no real strategic value at considerable cost in resources for the offensive only to be stuck behind yet another river.
Without "Arnhem" it would make more sense to attempt a direct river crossing of the Rhine.
They'd be stuck behind the Rhine if this occurred, yes. But the Germans would have been swept back behind the Rhine almost completely on the northern front due to the fact that the counterattacks would have been decisively dealt with due to the fact that Horrocks and XXX Corps would not be throwing off brigades in a head long rush for the Rhine to try to rescue the 1st AB Division and the Polish Brigade stuck in Oosterbeek. Instead, the Germans attacking Hells Highway would meet entrenched British Guards Brigades and well supplied airborne forces and be utterly destroyed in the attempt rather than in OTL when they met fierce resistance in some areas and cut the highway in others and the entire month of October consisted of Allied units with little to no cohesion fighting the Germans to the death over positions on Hells Highway to force them to retreat East or back over the Rhine.
What you would have in this scenario is the Germans entrenched on their side of the Rhine and Montgomery's troops holding their side fairly securely. What you might have is once Antwerp becomes operational, Montgomery is able to cross the Rhine in an amphibious assault similar to that which was eventually launched with Operation Plunder/Varsity, except instead of being done near Germany, it would be done in Holland. The US 13th and 17th Airborne Divisions would likely be ready to go by that point, as well as the British 6th Airborne Division, for the airborne portion, while the troops dropped in Market Garden could form part of the amphibious assault force along with the rest of 21st AG.
This operation could logistically be possible starting in late October at the earliest, but likely sometime in November. This might forestall the Ardennes Offensive, as Hitler would have a very real issue on the Northern flank and need to protect the Ruhr. I think that the initial assault, provided it could be logistically supported, would be very successful. The two German Panzer divisions in the area would be devastated by air raids during October as well as any fighting they should engage in, and the rest of the German Infantry in the area were as Allied Intelligence said, third rate at best. The force in Arnhem over the long winter was a combination of the Volksgrenadier remnants from the 15th Army, elements of Static and Fortress Divsions from the German Atlantic Wall defenses in Holland, ad hoc infantry forces levied from landlocked naval personnel and penal labor batallions, as well as the two SS Panzer Divisions. This is not a strong defensive force. Now, I am not sure how likely it is that this is even launched, as the idea would be for such a crossing to lead to a breakthrough across the North German plain, which is damn near impossible during winter. But still, the complete liberation of Holland was indeed an objective taken seriously by Allied Command, and a Rhine crossing was a target for 1944, not 1945.