People play years-long Traveller campaigns without advancement, so I don’t think it’s implausible at all!
I tried to make an overview of the alternatives at one point:
Besides advancement a campaign might be propelled by…
decline. A downward spiral. Delta Green or The One Ring do this.
character change. Fate with its milestones tries to do that.
an arms race. Shadowrun.
base building. The Ark in Mutant: Year Zero.
networking. Expanding a relationship map, watching it grow or change. Hillfolk is an example. Also maybe building reputation in a more resource-focused sense.
chronicling. Generational play in a year-by-year mode. Pendragon and The One Ring.
anthologizing. Episodes tied together by returning characters or factions. Remember Tomorrow has it.
changing the setting and/or mode of play. Kuro, Makkura, Kuro Tensei. The Veil, The Veil: Cascade, The Veil: Inheritance.
exploration. Hexcrawls or other kinds of strongly map-focused gaming.
investigation. Follow the clues. Trail of Cthulhu’s Spine or Night’s Black Agents Conspyramid.
questions. The Uniform Survey in Sign in Stranger.
railroading. Many a published campaign.