The gig economy is nothing new in itself, it was already present, the only thing these companies did is to make them “modern”. Here were not uncommon that people got some gig works to have the money for holidays (teenagers) or to round up salary from time to time.
It is not a problem per se.

The problem is that the gig economy is the only way to have a salary for some people, for various reasons.
That let the companies to pay way less because they have a big pool to choose from and have not any obligations (or advantages) to have a stable set of employees and to resort to gig workers only in peak times.
And that is true expecially in place like the US where the llabor laws are ridiculous.