... were the Sumerians the first? The first what? The article discusses the Uruk period, of maybe 4000 - 3000 BC.
In the middle east, there had been millennia of settlement and agriculture by this point. Gobekli Tepe is apparently ~9000 BC. The Tower of Jericho was built around 8000 BC. https://en.wikipedia.org/wiki/Timeline_of_prehistory
Circa 7500 BC there were a bunch of significant sites: https://en.wikipedia.org/wiki/Ayn_Ghazal_(archaeological_sit...
Did Sumerians not know about any of those preexisting sites in the broader region? Maybe they built bigger cities, but I don't think they lacked for evidence of older civilizations and sites.
The first to have a writing system, as mentioned in the article.
But quotemstr seems interested in something else, not specific to writing.
> Past empires, lost civilizations, and ancient artifacts have always fascinated us.
> There was no glorious but crumbled past empire to inspire them. They figured out everything for the first time, and we know little about what they thought about it.
I think the Sumerians were not without crumbled past ruins of civilizations that covered broad swathes of territory, though they may not have been "empires". But also, to us "the Sumerians" can seem like a brief period in time. But the Uruk period is almost a millennia in duration. For each individual, it may have seemed that the world changed very little over the course of their lifespan, and by 3100 BC, each city would have felt very old to its inhabitants.