Are the different laundry programs on a washing machine due to the design failure? My oven has separate knobs for temperature, heat distribution and grill; is that a design failure?

My car has both a steering wheel and a separate indicator light control; rain sensors and a manual wind screen wiper setting; light sensors and a manual setting for the headlights.

Are these all examples of designers' inability to make decisions?

Those all seem reasonable designs to me.

Often when that decision is made it is taken away from the user. For example when "There are decent sounding arguments for both" it is often exactly the right choice to leave the option available if it doesn't come at too much cost.

Often used ones aside options are generally so hidden away anyway and thus the choice of a sensible or popular default can be made regardless without complicating the main UX.

but if they are either mutually exclusive, or that one must be selected for the operation to work, then the designer/developer has to choose a default.

Often, the user don't even know what they want, and assume the default is the right choice, since it's "professionals" who have chosen it.

Of often they'll be unaware the setting exists or even more likely be unaware that the setting even _might_ exist (and therefore don't even think to Google it).

Though often still theyll be afraid to look around at settings for fear of breaking things.

not making the settings accessible is a design failure, imo