A civilization could not be sustained by a handful of people.
Port Nyanzaru was a perfect example. Although it possessed plenty of cutting-edge alchemical technology, magic streetlamps were currently the only thing that could truly be put into widespread use. Yet even magic streetlamps required a group of low- and mid-level wizards to inspect and maintain them regularly. As for the Golem Factory, which employed even more advanced alchemical technology, its routine maintenance required spellcasters numbering in the double digits. Whenever golems suffered damage and needed repairs, all that work also had to be carried out by low- and mid-level spellcasters.
Without these low- and mid-level spellcasters, Goria would have struggled to find enough time and energy for her research.
The same principle applied everywhere.
Cutting-edge experiments could rely on the talents of geniuses, but widespread implementation and maintenance required vast numbers of workers at the lower levels. The collapse of the Weave meant that the difficulty of Soren's Floating City project had skyrocketed. Losing so many low- and mid-level wizards would make even maintaining the Floating City extremely difficult in the future. The same held true for other civilizations. Scientists discovered all kinds of important knowledge, but advancing an entire civilization ultimately required countless workers and scholars.
The collapse of the Weave marked the arrival of the age of magiclessness.
Across the long history of the multiverse, the vast majority of eras that could be called an [interstellar civilization] had been built upon the Weave.
Without it, wizards would become figures shrouded in mystery.
Although there were not many wizards on the Material Plane at present, traces of them could be found in almost every town thanks to the Weave. But if the Weave ceased to exist, even large cities would rarely see a wizard.
Tap, tap, tap.
Soren